Well, idk. I'm pretty sure all mine handle heat just fine. I have a Lezyne 1000xl smart connect, niterider lumina 1200 oled boost and a Gemini Titan 4000 OLED, in order of power. The first two have batteries built in, the last one has an external pack. The Titan gets hot but has not in my experience so far stepped down to a lower power level. The niterider states in the literature that it will step down (so does the Titan) but in a year of use has not dimmed once. I rarely ever run the Lezyne light at full tilt, it's really used mostly as a dtf light on my monster cross bike but the times I run it at night at full it dims Because it's running out of battery but not because it's hot.
I usually don't use any of these lights during the summer because it's light out 'later' but I have never had any of them dim on me. I've been riding when it's pretty hot at night with all of them and never had an issue (Arizona, not summer hot but in the fall, still hot af)
Hope this helps