I went to replace a bad ballast in one of the steeple lights at one of the church buildings I look after.  Thinking that the construction contractors for the building, which was built around 2009/2010 had put in regular 100 Watt HPS fixtures for the steeple lights, it didn't occur to me that these were actually 100W MH fixtures until I got up onto the roof and took one of the 2 fixtures apart.  There was no label on the reflector/lens to indicate Metal Halide, just 100W.  Well once I pulled the cover off, I was greeted with a very nasty burnt up ballast smell and surprise surprise, it was a metal halide ballast, which means someone put in a 100 watt HPS bulb when the original 100W MH bulb burned out.  So no wonder the ballast went out.  Not to worry, I brought with me a new 100W HPS ballast and proceeded to change it out, getting some of the "oil" residue from the burned out ballast and smell all over me in the process.  That stuff is NASTY.  So out came the burned up Universal 100w MH ballast and in went a new Sylvania 100W HPS ballast with capacitor and starter.  The other light on the other side of the roof also has a 100W HPS bulb in it, likely running off of the original 100w MH ballast, so it's just a matter of time before that burns out as well, but I was too tired and worn out to replace it.  Now I'll admit that white light looks MUCH better on the white steeples as compared to the orange light of HPS, however given my dislike of the short life span of the MH bulbs, I'll eventually end up taking out the ballasts and putting in 175W equivalent output LED bulbs in those fixtures and the same at several other buildings so as to give a good white light but with hopefully a long 20,000-40,000 hour life.  Some of the roofs are tile roofs and I crack the hell out of the tile every time I get up there.  Can't run a Mercury Vapor setup either, against "energy savings" guidelines that we have to follow 

Locations such as that would have been perfect for /DX mercury lamps. The most reliable and long lived...but no. Stupid energy laws/bans make for a crappy selection. Even HPS aren't always as reliable as MV. I guess LED's are supposedly getting better and affordable but meanwhile we are stuck with MH for white light and those tend to be quite problematic unless you get lucky and run across a good batch of lamps, but that's like playing the lottery, lol. I use some 100w MH floods at work and sometimes lamps go for a year or two or they might go for a month or two.

If you go LED, don't use retrofit lamps. The heat dissipation in an enclosed fixture is very poor and you won't get nearly 20,000 hours out of them. I suggest replacing the fixtures with new LED fixtures.

I went to replace a bad ballast in one of the steeple lights at one of the church buildings I look after.  Thinking that the construction contractors for the building, which was built around 2009/2010 had put in regular 100 Watt HPS fixtures for the steeple lights, it didn't occur to me that these were actually 100W MH fixtures until I got up onto the roof and took one of the 2 fixtures apart.  There was no label on the reflector/lens to indicate Metal Halide, just 100W.  Well once I pulled the cover off, I was greeted with a very nasty burnt up ballast smell and surprise surprise, it was a metal halide ballast, which means someone put in a 100 watt HPS bulb when the original 100W MH bulb burned out.  So no wonder the ballast went out.  Not to worry, I brought with me a new 100W HPS ballast and proceeded to change it out, getting some of the "oil" residue from the burned out ballast and smell all over me in the process.  That stuff is NASTY.  So out came the burned up Universal 100w MH ballast and in went a new Sylvania 100W HPS ballast with capacitor and starter.  The other light on the other side of the roof also has a 100W HPS bulb in it, likely running off of the original 100w MH ballast, so it's just a matter of time before that burns out as well, but I was too tired and worn out to replace it.  Now I'll admit that white light looks MUCH better on the white steeples as compared to the orange light of HPS, however given my dislike of the short life span of the MH bulbs, I'll eventually end up taking out the ballasts and putting in 175W equivalent output LED bulbs in those fixtures and the same at several other buildings so as to give a good white light but with hopefully a long 20,000-40,000 hour life.  Some of the roofs are tile roofs and I crack the (...) out of the tile every time I get up there.  Can't run a Mercury Vapor setup either, against "energy savings" guidelines that we have to follow 

why don't you just put in an induction fixture? looks like mercury vapor DX, efficient as LED.

see if something like this meets your specifications:

http://www.everlastlight.com/outdoor-fixtures/classic-flood-light-fixture.html

Are you using ceramic metal halide (CMH) lamps or standard MH lamps? The CMH lamps seem to perform better, particularly in horizontal burn applications.

I'm guessing they are standard.  These are what I put in the MH Fixtures (the ones I am not converting over to HPS, such as what I have shining up on flag poles and white steeples.  some are horizontally mounted, others are vertically. 
http://www.elightbulbs.com/Sylvania-64479-M175-U-MED-Metal-Halide-Light-Bulb
http://www.elightbulbs.com/Sylvania-64417-MP100-U-MED-Metal-Halide-Light-Bulb

Most are medium base, a few are mogul.  why such crappy life out of these things?  10,000 rated hours is stupid. 

I'm converting many of the 175Watt MH over to 150 Watt HPS.  I get great life out of these, often upwards of 30,000 hours in many cases.   
http://www.elightbulbs.com/Sylvania-67508-LU150-55-MED-High-Pressure-Sodium-Light-Bulb

The white color on the flag is essential and on some of the Steeples as well.  The perimeter and parking lot lighting does great with HPS. 

Hope you're not actually buying those from eLightBulbs. That site is a good place to find obscure lamps but is overpriced on the common stuff.

Hope you're not actually buying those from eLightBulbs. That site is a good place to find obscure lamps but is overpriced on the common stuff.

Nope.  I just use that site as a reference.  When given enough notice, the facilities group is able to purchase the bulbs from a Sylvania dealer or directly from Sylvania using special pricing.  When something is needed right away, the mechanics usually go to Grainger which means they end up with GE Products.  (overpriced but they get it when they need it) 

I just tried to post a reply, but it seems to have gone to the magical internet void, so I'll rewrite it.

The M175/U/MED is a standard 175 Watt probe start quartz MH lamp, and they usually have a short life regardless of the manufacturer. The only other option is to upgrade the ballast and lamp - 150 Watt HPS is a good choice where color rendering isn't important.

The MP100/U/MED is a 100 Watt pulse start quartz metal halide lamp that is rated for 15,000 hours vertical, 10,000 hours horizontal.
Ceramic metal halide lamps are pulse start and generally have better light quality and longer life than quartz lamps. Some 100 Watt ceramic metal halide lamps are:
-Sylvania MCP100/U/MED/830 (20,000 hour rated life)
-Philips MHC100/U/M/4K/Alto (20,000 hour rated life)
-Philips MHC100/U/M/3K/Alto (16,000 hour rated life)
-GE CMH100/U/830/MED (rated 15,000 hours horizontal, 10,000 hours vertical) not sure why they have a shorter rated life compared to others

There are also Eye Moon Pulse lamps which are mercury lamps designed for use with pulse start metal halide ballasts for architectural lighting. They provide less light than metal halide bulbs, but they cost less and still have a 16,000 hour rated life.

I greatly appreciate that information!  It will prove to be most helpful.  THANK YOU!!

Glad to help!

I went to replace a bad ballast in one of the steeple lights at one of the church buildings I look after.  Thinking that the construction contractors for the building, which was built around 2009/2010 had put in regular 100 Watt HPS fixtures for the steeple lights, it didn't occur to me that these were actually 100W MH fixtures until I got up onto the roof and took one of the 2 fixtures apart.  There was no label on the reflector/lens to indicate Metal Halide, just 100W.  Well once I pulled the cover off, I was greeted with a very nasty burnt up ballast smell and surprise surprise, it was a metal halide ballast, which means someone put in a 100 watt HPS bulb when the original 100W MH bulb burned out.  So no wonder the ballast went out.  Not to worry, I brought with me a new 100W HPS ballast and proceeded to change it out, getting some of the "oil" residue from the burned out ballast and smell all over me in the process.  That stuff is NASTY.  So out came the burned up Universal 100w MH ballast and in went a new Sylvania 100W HPS ballast with capacitor and starter.  The other light on the other side of the roof also has a 100W HPS bulb in it, likely running off of the original 100w MH ballast, so it's just a matter of time before that burns out as well, but I was too tired and worn out to replace it.  Now I'll admit that white light looks MUCH better on the white steeples as compared to the orange light of HPS, however given my dislike of the short life span of the MH bulbs, I'll eventually end up taking out the ballasts and putting in 175W equivalent output LED bulbs in those fixtures and the same at several other buildings so as to give a good white light but with hopefully a long 20,000-40,000 hour life.  Some of the roofs are tile roofs and I crack the hell out of the tile every time I get up there.  Can't run a Mercury Vapor setup either, against "energy savings" guidelines that we have to follow 

The reason that the ballasts were overheated was because North American 100w S54 high pressure sodium lamps have an arc voltage drop of only 55v whereas the North American 100w M90 pulse start metal halide lamps have an arc voltage drop of about 100v. The low arc drop from the high pressure sodium lamp caused the ballast’s core to saturate and overheat from the stress caused by operating the low arc voltage high pressure sodium lamp on the 100w M90 pulse start metal halide ballast. It is good to note that European 100w high pressure sodium lamps will run nicely on North American 100w M90 pulse start metal halide ballasts without overheating because those high pressure sodium lamps have an arc voltage drop of about 100v just like the pulse start metal halide lamps do. Even though European 100w high pressure sodium lamps are electrically interchangeable with North American 100w M90 pulse start metal halide ballasts, it is not recommended to use them in commercial settings because you can be still be sued for operating the “wrong” lamp in the fixture after a property inspection even though that lamp works properly without overheating the ballast.