"Michael" wrote:
Light bulbs have a very long MTBF, especially DC bulbs.

Depends how you run them. If you're trying to get the most illumination
for a given electrical power, you run them at full rated voltage and get a
relatively short lifetime. On the other hand, if you run them at less than
rated voltage, you get much lower conversion efficiency, but also much
longer lifetime. I'm guessing that most panel lighting bulbs are run this
way.