> Inadequate ventilation, allowing excessive heat build up?

Open metal housings

> Large spikes on the power line?

Horrible coincidence if there's one always EXACTLY at turn on

> Multiple hard on/off cycles?

Once on at sunset, once off at bedtime. That's about as kind as
you could be

> Excessive vibration?

Fixed firmly to walls and ceilings

> Seems to me that it would be far better to correct the problem
> than to waste 5% or 11% of the electricity you are buying

I agree, if there was an identifiable cause other than the obvious
wear and tear through under-rated manufacturing. I betcha bulb
mftrs could make bulbs last a damn sight longer if they wanted
to. Resistors are an acceptable $10 one-off alternative to spending
$50 a year on replacement bulbs. Besides, as the brightness
hardly changes, what's the diff ?

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