I have found the solution to ALL your problems, well concerning flight time that is for M4P.
its a little expensive, but I bought this battery here, and it lasts forever. They claim 50min. i got bored during my test and landed. so yeah its long!
I am a recent owner of a Mini 4 Pro. I had lot of doubts about battery duration. Now I will share here my happy experience.
Using an original PLUS battery from DJI (beware cheap fake copies on the market) I got 29 - 30 minutes of flight time landing at 12% - 14% remaining.
For my point of view that is a fantastic duration. About identical the only two flights I did on a Mini 3 (no Pro) before returning it and much more than the 22 minutes my old DJI Mini 2 used to do.
Take into account you can squeezy this PLUS battery a bit more than standard battery and still conserve a secure flying returning home time.