I have been using an L1Tv2.0 RB80 with - first - a 14500, and, later, after getting a P2D body and tailcap and an RCR123a, with - thus far, as far as I can see - no ill effect.
As others have said, there's no low, but a high and a turbo mode. This is also what I prefer, so for me it is a perfect EDC. It now rides in an AJC Concealco leather holster on my left hip.
It seems as the most common problem with the LxTv2.0 RB80 is the forward clickie - that I prefer to use - that seems to fail for many users. I dismatled the tailcap and soaked the switch with gun oil. For about a week or so, the light flickered quite a bit, so I wondered if I did the right thing, but after that it seems to have recovered, and now functions smooth and without any problems.
About two weeks ago, I ordered an L1Tv2.0 Q2, a P2D body and tailcap from FenixStore, to keep as a spare, as I like this configuration very much. Haven't received it yet, though, but that might have to do with a cross-antlantic shipping, customs, front wind, or whatever ...