Doesn't it always seem like light bulbs expire at startup rather than during operation? That's how it has been in my experience. I come home from work, turn on a light, and pop! The light bulb burns out the instant after I turn it on. (That is, that's what happened when I used incandescent light bulbs. I now use compact fluorescent light bulbs and have not had to replace one yet)
It's not a mystery why
light bulbs fail upon startup rather than during operation. Light bulbs contain a thin tungsten filament which when pumped full of electric current heats up extraordinarily hot and produces light. As time goes on and the light bulb is turned on and off, the tungsten filament in the light bulb begins to oxidize. This means the filament begins to rust and generally weaken. Over time this greatly compromises the filament, which has to withstand voltage overload every time the light switch is turned on.
Eventually the startup voltage overload becomes too much for the filament and it breaks. That's one way an incandescent light bulb can fail; another is due to an uneven filament. As the light bulb is used, certain points along the tungsten evaporate and thin out the filament. This can also cause coils of the filament to get pushed together. Heat builds up significantly faster in the thin areas of a filament, or where coils are pressed together. This extra heat becomes too much and the filament breaks or even melts.
It's the initial stress on the tungsten filament that leads to an incandescent light bulb's eventual failure. It seems like light bulbs are engineered to work best when operating 100% of the time, with no mind to the stresses and strains of overloaded voltage at startup. On the energy efficient side,
compact fluorescent light bulbs do have filaments, but they are tiny and used at a much less intense level than incandescents. I'll have to do some investigating to see how compact fluorescent and LED light bulbs go through the failing process.
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