> Does anyone know of longevity curves for LEDs pushed beyond
> spec?  Does it depend soley on manufacturing specifics?

Just out of interest and kind of related...........

Lumiled (Agilent & Philips venture) have a range of 1W 180,000mCd
super-emitters with 100,000 hour rating and a white 5W with just 500
hours life @ 700mA. An important factor is the size of the heatsink on
the back of the LED

http://www.lumiled.com/luxeon/products/emitter_index.html

It's been mentioned here before that heating is a sign there could be
stresses on the LED.

From Lumiled about the 5W Star V Portable  - "The maximum rated
temperature of the PC board is 70C, however a heatsink temperature
of 35C is required to retain a 90% lumen output after 500 hours". Note
that these extreme LEDs are rated in watts, maybe you should use
similar calcs on the ones you're using

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