This heat thing keeps coming up. I've seen all sorts of things suggested: that the old models are in boxes, the new ones in blisterpack, that you have to use a dummy cell, etc., etc.....
Please note this thread, where I posted the "official" answer from Streamlight on the heat issue. IF you have one that's heating up, instead of going out of your way to figure out solutions, just SEND THE LIGHT BACK and Streamlight will replace it with the latest (updated) fix for the heat issue.
The thread (and answer from Streamlight) is here>>
Streamlight 4AA heat thread