Hi,
I recently purchased an m5paper. Yesterday I worked up a tiny app in uiflow to get the net time once a minute and power off the rest of the time with it displayed. It ran for over 14 hours on battery. If there was a way to avoid the restart screen, it would probably run an hour or more longer.
Also this past week, I created a chess tool, where I can move the pieces (graphics copied from a Github page) about and save/recall the board state using the EEPROM. It is over 500 lines of inefficient python code. I discovered that there is a filename length limit to png files e.g. black_bishop.png is too long so I shortened it to blk_bish.png.
I also discovered that the uiflow page is too tall for my MacBook Air if I want to see files on the m5paper UI (left) side of the screen.