Two questions re LED MTBF and coated lens

1) What's the average life (MTBF) of LED modules found on Ultrafire/Romisen type flashlights ?

2) Do the "Multi-Layer Coated HD Flashlight Lens" found at KD (Flashlight DIY section) make any difference ?

3) I will be carrying my SS UF C3 in my backpack most of the time. Should I worry about the glass lens getting scratched ?

Thanks.

This doesn't help much, but:

1) Don't know. When driven at spec current (350 mA) with a good heatsink, the LEDs will last 10's of thousands of hours to 50% efficiency. The UF/Rom and other DX/Kai light LEDs are driven at various voltage levels with unknown level of heatsinking (probably including none). High temperatures can reduce lifetime drastically, and no one's done testing on any of those lights to know for sure. I doubt the 1AA lights can overdrive them much (but I don't know about their heatsinking). Direct drive RCR lights might, but effect has not been measured.

2) People seem to think so. Most of the light reflected by uncoated lenses does get out of the light, it just gets diverted from the hotspot to the spill by multiple bounces. People seem to measure about a 10% increase of hotspot lux with a good coated lens.

3) I wouldn't think so unless you've got lots of sharp metal objects back there. If it's really a worry, slip the light into something before you toss it into there.

OK, thanks.

Oh...and welcome to CPF! Pretty soon you'll have so many lights, LED lifetime won't be much of an issue with you...