I've used the M6 constant-on several times until the batteries are used up to test out runtimes and never experienced "Thermal Shutdown".
It is usually outside at night when the temperature is not that warm. On a family holiday earlier this year I let two of my young cousins use an M6 each (with MN20 lamp), while I had a third with the MN21 lamp. We were playing a 'wide game' (kinda like hide & seek) and used a lot of SF123A's that night. I also had my cousins using two 10X's, two M4's (MN60 lamps) and two M3T's (MN15 lamps). Most of my cousins are about 6-15 so they had little understanding of how expensive the torches were and ran them pretty much constant-on except when they had to flash them only when they thought they had a member of the opposite team in their sights.
The game involved two teams - one with flashlights who stayed in one spot, and the other trying to get from point A to point B. One of the ones with a flashlight would shout "Freeze!" and then shine the flashlight where they thought one of the opposition was. If they were caught in the beam then they were out, if not then the whole advancing team got 10 seconds to move or hide when not lights would be on. We used a 'wild' area of light small trees and scrub - lots of places to hide.
Anyway, the only flashlight I've experienced Thermal Shutdowns with is those powering the N62 lamp (12PM, M4 etc)
Al
