Maybe my memory is foggy, so after MarcinP's comment, i think i was wrong about the charging time. I am so sorry.
MarcinP: There was any trouble with the donwgrade of MAX? (7 to 6)
I have installed android 7 but December firmware is including latest screen drivers and new camera app (if I correctly remember)
The best way is just install latest one and test everything. If you have any issues then you can try other ones.