Olight batteries are top notch. I'm 10% of the way through the 500 charges listed for the Olight S1R battery form completely dead, to fully charged, just over 50 full from dead charges. Since I got the SMini Ti some time ago it replaced the S1R for daily carry. It's been sitting two weeks and I just checked it. 4.20V. Hasn't dropped any since it came off the charger.
For 18650s I run the streamlight branded cell. It runs a tad shorter than higher mah batteries but it runs at full brightness longer then fades quicker. Where the higher mah batteries I've tried dim quicker but run slightly longer. I'm more into full brightness at a longer time than pure run time with dimmer output along the way. They aren't super expensive either. Very good 18650s.
i have a pair in my MT40GT and it just runs and runs and keeps going. I don't see a need for anything else.