It surprises me how slowly I speak and how bad my timbre is, it is painful to listen to it, sorry. :)

Forever, if possible :)

I think low mode is the only commuter friendly mode.

Yepp, it does heat up quickly on high mode in room temperature. I'd say high mode of the 8x7135 version is only for in case of necessity: when you need it, you have the possibility to use it on maximum for a few minutes. (Medium mode seems almost the same bright for your eyes anyway). Of course, in cooler temperature (~below 10 C) you don't really have to pay attention to overheating.

It will automatically drop brightness when it gets to 50°C