Here we go again. /ubbthreads/images/graemlins/smile.gif Do some searches. It has been discussed practically to death. But to save you some time looking:
Any flashlight advertised as using a 5W white LS would be using one of those. 500hrs is the half-life of the LED, ie it will be half as bright as new when it has been run for 500hrs. Incandescent bulbs are rated for the time they burn out, not half-life.
Considering how much people want the latest, greatest, brightest white LED flashlight and the usage pattern of such bright lights (you'd be pushing to average 5hrs a week and think of the number of cells you would go through for just those 5hrs), and the fact that they find a mere 100hrs of incandescent bulb life as adequate, LED-modders thought that it would be acceptable to use the 500hr LS until such time that better LEDs become available.
All 5W mods I know of are made so that the LED can be swapped out without too much dram when the time comes; the one concession a good modder has to make when building 5W LS flashlights. I haven't opened a SF L4 or similar, but I understand that it is the same there.
5mm LEDs driven at nominal spec are expected to have a 100,000hr half life, though many are overdriven so expect a reduced half-life, maybe 50,000hrs. IIRC, the original half-life of 5W was advertised as 50,000hrs. This was quickly reduced to 5,000hrs then to 1,000hrs and finally to 500hrs when it was found that the heat was cooking it to death and they could not achieve the full rated life.
Roy123: I believe the 2 datasheet merely reflect the two available versions of the 5W LS, one being the bare die-on-slug, the other being the die-on-slug-on-aluminium heatsink. I'll need to check to be sure. Can you post links to the actual pages you are talking about?