There's been quitw a lot of discussion on this subject in the past.
Lumileds max spec current is 700ma.
I like to run mine in
m@glite mods at 1000ma - The hotlips / aluminium mag body does a great job of wicking heat away from the emitter. (Even with good heatsinking emitter life will be reduced)
Lux V's will put up with abuse for some time before they give up the ghost............
I have a 'U' voltage Lux V which I have running direct drive from 6xAA Nimh's - This pushes 1600ma !! through the emitter.
Its great as a demo light for 'wow' factor but I wouldnt use it for more than a few minutes at a time.
Even then - at this current I dont expect it to have a particularly long life....Though we're still talking a damn site longer life than most incan's.
Mr X's 'Space Needle' runs at around 1500Ma too.
Tim