Are 50,000 hours lifetime realistic?

[BrightMan]

Most of the LED's in flashlights are rated to 50,000 hours lifetime.
But is this lifetime related to an average use of the different brightness modes or to the highest mode?

For example, if I would use a Fenix TK40 50,000 hours non-stop ONLY in turbo mode, would it really run for 50,000 hours, until brightness dimmed to 50%?

 

[Moonshadow]

Considering that's nearly six years of continuous use (not allowing time for swapping batteries !), it's probably largely academic. As a good CPF'er you should have upgraded at least six times by then anyway !

Speaking of changing the batteries, a set of 8 (yes, 8!!) AAs will give you two hours on Turbo, so that's 25,000 battery changes, or 200,000 batteries !!! oo:

Somehow, I think the lifetime of the LED is going to be the least of your worries !

 

[american lockpicker]

Led Lenser claims 100,000 hours for their LEDs

 

[Saint_Dogbert]

Yes and no. As far as I am aware the output of any LED will gradually decrease over its lifetime, but will be within certain tolerances for those first 50,000 hours. An over driven LED will probably dim faster, and perhaps suddenly die sooner, too. It won't be a problem though. Even if you use a light for 2 hours straight a day, every day, even if the life of the LED is cut in half from the high output, you're looking at 20+ years of service.

 

[rmteo]

As long as they are not overdriven, 50,000 hours is valid. The key is temperature control - this is from the Cree XR-E datasheet:

Lumen Maintenance Projections

Based on internal long-term reliability testing and standardized forecasting methods, Cree projects XLamp LEDs to maintain an average of 70% lumen maintenance after 50,000 hours, provided the LED junction temperature is maintained at or below 80°C.

 

[Wiggle]

As long as they are not overdriven, 50,000 hours is valid. The key is temperature control - this is from the Cree XR-E datasheet:

And even a fairly overdriven LED still has a ton of burn time when you think about how intermittant typical light use is and how quickly we typically upgrade anyway.

 

[BBnet3000]

this sort of thing is definitely more of an issue with fixed lighting than flashlights. i buy my flashlights to last, and its likely that i will age faster than my flashlights will.