Why I ask, is I was walking past a shop the owner was changing the T12 tubes, in a sign it had 3  4foot tubes, only one tube was still working, and it looked very tired, he said the fitting was never turned off
and the fitting was last opened 11 years ago when new tubes were fitted, do you think it is possible for tubes to last that long ?
 
 

11 years would be over 90,000 hours. I think that is pushing the limit, but I think it may be possible on 24/7 operation. I would expect the phosphors to have dimmed a lot though. I assume the fixture was magnetic preheat (switch start over there)?
I have seen 50,000 hours out of a Sylvania F40/DCWP, and even though that is in the U.S. it should also be possible in New Zealand.

I have seen a odd westy blackender in a brake room up stairs in a old albersons since i was a kid as long as u remembered that t12 blackender held up until HEB took that store over, that lamp saw 24/7 service over 20 years but bit dim but lighting the break room.  From
There if dont even lnow if it still there or not
Cause they block that area off as employee only.
It prolly got way over 150,000 hours on them.

Yes 90,000 hrs is a lot, but the guy did seem very genuine,  the one tube that working was still was very dim with very dark ends yes the fitting did have starters ,very interesting the hours these  lamps can do.

Some say as the subway station between West- and Eastberlin, which was walled due the Berlin-wall in 1961, opened in 1989 , workers saw there a hidden room lit by one flourescent tube T12 40W by opening the station. Noone knew from where the electrical power came, but the tube was there and shined and the room was untouched for 28 years!

I personally believe flourescent tubes as also mercury vapour lamps can run way more than 100000 hours, but only if they run all time. Here we say "Every switching kills the lamp a bit more "  Even when they work 100000h or more, they'll lose that much intensity of light that you normally replace them.

By the way, 2012 i got two very used T12 40w FTs made in 1957 which seem to be not able to light or even flash, but if you turn out all light you'll see them in a white extremly dim glow.

By the way, 2012 i got two very used T12 40w FTs made in 1957 which seem to be not able to light or even flash, but if you turn out all light you'll see them in a white extremly dim glow.

That means the cathodes are either broken, or the emission mix is completely not working. The glow means there is slight ionisation from the capacitive current.
If the filaments are complete, you may try to ignite it on some electronic ballast: It could well be the cathodes need to reactivate after the too long storage.

Magslight, Love your story about the hidden room and the light.
Looking back I should have asked the guy for the lamp that was still working, after its great effort it
deserved to be saved, I think most of you, would agree with that.

The old British Atlas 'SUPER' range of T12 tubes from the 1960's (SUPER FIVE 5', SUPER SIX 6' and I think they also made a SUPER EIGHT 8') were designed to give decades of service. I managed to find a few at a demolition shop here that have had mininal use, but in the pile was one that, although still works well, has such heavy ageing on it I'm sure it was run 24/7 for many years. See here .

Some say as the subway station between West- and Eastberlin, which was walled due the Berlin-wall in 1961, opened in 1989 , workers saw there a hidden room lit by one flourescent tube T12 40W by opening the station. Noone knew from where the electrical power came, but the tube was there and shined and the room was untouched for 28 years!

The way I heard this story it appeared as if it referred to the suburban train system, which had one such transit line with four closed stations. If the subway system has to be added: Two further transit lines with together ten closed stations.

Well, if so the power simply came from the lighting circuitry around, but I have my doubts if really a lamp remained forgotten and was still burning after about 250,000 hours. All details, starting with the basic one of the exact location, remain unclear, and thus I would not rule out the scenario that guards still entered the room in question and changed the tube when necessary.

I read somewhere that a rapid start fluorescent loses about three hours every time it is turned on and off, instant-start takes off about 3 hours, and an HID takes off 10 hours! So if you had, say, F32T8s on electronic instant-start ballasts, or F96T12 slimlines on motion sensors in a public restroom, they wouldn't last very long compared to if they were running 24/7 except for maybe the occasional power outage.

I'm gonna be doing a comparison soon with 2 identical fixtures, one running 2 new F40T12 tubes on a new T12 Magnetic rapid start ballast and one running 2 new F32T8 tubes on a new T-8 electronic rapid start ballast.  These fixtures are wired to stay on 24/7 as they are "security" lights for stairwells in my church building. 

Hi, Ryan that will be an interesting comparison , its good there both double fittings , I would put my money on the T12 magnetic
I would say it will be some time before we get the results.

I read somewhere that a rapid start fluorescent loses about three hours every time it is turned on and off, instant-start takes off about 3 hours, and an HID takes off 10 hours! So if you had, say, F32T8s on electronic instant-start ballasts, or F96T12 slimlines on motion sensors in a public restroom, they wouldn't last very long compared to if they were running 24/7 except for maybe the occasional power outage.

An interesting comparison from a datasheet of PHILIPS MASTER PL-L 36W/840/4P 1CT.

Life to 10% failures EM	10000 hr
Life to 10% fail Preheat EL,3h	14000 hr
Life to 10% fail Nonpreh EL,3h	7500 hr
Life to 50% failures EM	15000 hr
Life to 50% fail Preheat EL,3h	20000 hr
Life to 50% fail Nonpreh EL,3h	10000 hr
LSF HF Preheat 2000h Rated,3h	99 %
LSF HF Preheat 4000h Rated,3h	99 %
LSF HF Preheat 6000h Rated,3h	98 %
LSF HF Preheat 8000h Rated,3h	97 %
LSF HF Preheat 12000h Rated,3h	94 %
LSF HF Preheat 16000h Rated,3h	82 %
LSF HF Preheat 20000h Rated,3h	50 %
LSF EM 2000h Rated,3h cycle	99 %
LSF EM 4000h Rated,3h cycle	98 %
LSF EM 6000h Rated,3h cycle	96 %
LSF EM 8000h Rated,3h cycle	94 %
LSF EM 12000h Rated,3h cycle	80 %

Note: This is a typical lamp used in streetlights in smaller towns/villages here. They run on a magnetic ballast.

Oh yes.  The instant start equipped fixtures in the bathrooms at my church buildings that have motion detectors/heat detectors most certainly burn out MUCH quicker. 

In that case it would be best with magnetic rapid start F32 ballast or 2nd choice programed starts