You will probably be very happy with your TK41. After using mine for a few weeks, I am finding I like it more and more all the time. Really puts out a wall of light and has great throw. Hard to believe that it's only using AA NiMh batteries.
One of the things I'm finding is I really like the different modes. Low mode is only listed at 10 lumens but it is surprisingly bright and throws a long way for 10 lumens. It's supposed to run 10 days on low.
Medium is listed at 108 lumens for 27 hours. I am finding this is more than enough light and throw for almost anything I will be using this light for.
High is listed at 335 lumens and 7 hours 15 minutes of burn time. I find this looks brighter and throws quite a bit farther than my Olight M20s R5 which is listed at 340 lumens. On this high setting, this TK41 is on par with my Jetbeam BC40 at 830 lumens as far as the throw goes.
Switch to Turbo and this sucker kicks into overdrive. Not as much throw as my Olight M3X Triton but it's not far behind. My only complaint is that so far I have not found any of my AA NiMh batteries that will give me close to the 2 hour 10 minutes run time when the light is on Turbo mode.
One small concern is the battery holder. I wish it was a little stronger. I don't know if this will be a problem in the long term or not. So far, no problems. I emailed Fenix and asked them if I could buy a spare battery holder 10 days ago. I have not received a reply yet. I guess I will try again.
I do notice a little wiggle of the battery holder inside the battery tube when I move the flashlight quickly but it really doesn't bother me.
Over all, the TK41 is a great light and has more than surpassed my expectations.