What most people seem to forget is that 'turbo' as in 'turbo boost', is only designed to be used for a few minutes. It the light was supposed to run at that brightness for longer, it would have been called 'high'. If one looks at the graphs that may, they make more sense. I realize that there is not a 'turbo' mode as such on the Tool, but the curve displays the same behavior that turbo modes display on other lights.
Also, I don't worry so much about the not exactly flat regulation of high mode. I plan on using my Tools as close in area lights, and for that medium is more than enough, and high gives me that extra little bit if I do need it.
As for using a 10440 cell, there has been a lot of discussion lately on both forums about that. The consensus is that with using a 10440 one will not let the magic blue smoke out immediately, and the light will produce a brighter output. However, the consensus is also that after a period of use, the light will no longer switch to the lower modes, and one can no longer revert to a AAA cell. It also seems to shorten the life of the LED due to the increased heat. I know I tried it on one of my Tools, and the big thing I noticed is that the apparent spacing of the modes seems to be compressed, so that there is no real 'low' mode anymore. That actually makes sense, because remember that it takes a four fold increase in output to produce a two fold visual increase. From the measurements I noticed that the jump in output between the three modes is 4x, which would produce a nice visual doubling with each step up. Now increase the voltage, which produces a linear increase in output in all modes. All of a sudden the modes are not separated by a 4x increase or decrease, and the visual perception reflects that. Also, the head did get noticeably warm after only a few seconds of use (less than a minute). I will stick with my AAA cells, which right now are Amazon Basics LSD.