As much as I like Sylvania for their long lasting, American made bulbs, I've noticed that some of their bulbs have chips and cracks in the glass.  I got some A15 60 watt ceiling fan bulbs today.  One of them had a noticeable chip in the glass.  I'm wondering if these chips in the glass lead to air leaks and thus make the bulb burn out prematurely.  I had one of them burn out in under a week in a ceiling fan fixture.