How do they calculate the time an LED will last?

How do they truely calculate the time an LED will last?

I had my fenix P2d ce come on in my pocket, talk about a pocket warmer! I wonder if any damage might have been done to the board. It was pretty hot, when I got it out.

It just got me thinking about the life of the LED.

Re: How do they.....

Short answer, thousands of hours of testing, and a very good understanding of the degradation process of the component chemicals in the particular method used to construct the LED in question.

Re: How do they.....

The degradation of LED's is exponential. During the first 10,000 hours it may loose 1% output, then during the next 10,000 it could loose 4% and then another 16%, etc. However, if it is not heatsinking properly, the curve is drastically shortened. This can be shown by not heatsinking a high power LED (not recommended!). It will last a few hours, if that, at a highish drive current (700ma?). However, properly heatsinked, it will last a lot longer. When you overheated your P2D, you moved along the curve more than the amount of hours it was running for would suggest. This may be significant, but it probably isn't. 50,000 hours is 5 years constant on, give or take. Even used a fair amount (average of 2 hours use per day), that's still 60 years to 70% with decent thermal management. With the occassional overheat like you experienced, I can't imagine the life of the emitter would have shortened noticeably.