Been using my DFT and SF brand 18650's since May, on patrol.
Had some inconsistent results early on, but I didn't do any consistent testing of it, either, so can't say for sure what was happening. One of the issues I noticed was the light shut off after about 20-30 minutes use while I was on a call and had the light on for awhile . I theorized that it was due to my using gloves (Mechanix), which held the heat in, and thus the light shut down, but it may have been that the battery was partially depleted to start with.
Since then, I've tested each of the 3 batteries 2x each, starting from a full charge, with a stopwatch running.
All three of my SF 18650s will run the light at 100% brightness for about 90 to 95 minutes, and then the brightness starts fading over about 5 minutes, and the light shuts off. Ambient temp was about 70 degrees. One of the tests I wore the same gloves, and kept the glove to the bezel to see if that affected anything. It didn't.
The bezel gets pretty warm, reaching the highest temp at about 10 min, and remains that way for the remainder of the 90 minutes. It's not too hot to touch, but you won't want bare skin touching it for a prolonged time. I just move my hand slightly away from the bezel.
I'm very happy with the DFT and will buy others, and also the Scout variant.