I love using a 10440 in my Liteflux LF2XT. It's expressly designed and optimized to handle them. Unlike a lot of other lights, the LF2XT does not shine like a super nova on max with a li-ion cell. It is designed to be bright but not so bright that it causes any harm to the emitter or the cell. Consequently, it has good runtime on max with a 10440 and can be run on max till the light shuts off due to the battery running down without fear of damaging anything.
Plus, it has some very cool features to protect these somewhat delicate cells, such as over discharge protection (which is especially important for 10440's as most are unprotected), and the ability to provide a "voltage report," (i.e., "display" the voltage remaining in the cell on demand to three places (e.g., 3.75) with a sequence of flashes).
When one combines features like that with a programmable UI (available if wanted but not required to be used), plus what many regard as a perfect beam and tint, it's easy to see why my LF2XT has become my favorite light even though it only is a lowly single AAA light, and why I'm looking forward to their next release of a new single AA light, which I'm hoping will be released before the end of the year.