My battery duration seems longer: the program I ran Tuesday is still running "more or less". By "more or less" I mean that sometimes I find the M5 with a black screen, and I have to press the POWER ON button to wake it up. I shouldn't need to do that, so this strange. But at least with the counter displayed on the screen, I know my program ran for 72 hours (indeed more or less 3 days).
Difference with yours:
I do not connect to a Wifi / Internet (which usually consumes battery quite a lot)