Just for fun, I put the thermocouple sensor from the prototype of my battery/led/driver analyzer (Any interest in a LED/Battery analyzer device?) on the head of one of these flashlights/coffee warmers (with a fully charged Panasonic 2500 mAh battery) and switched it on high. Within one minute it was at 100F. After 10 minutes it was 143F. Temp peaked at 160F/70C at 72 minutes when the battery started being depleted.
One interesting thing was a short 3 degree F drop in temperature every time that I walked by it. A little moving air does wonders for cooling.