Overall I find the battery life of the M4 iPad Pro to be awful. It seems to drain itself at an alarming rate even whilst just browsing the web. I think Apple a mistake fitting the M4 chip in it, I am fairly certain my old M1 was a lot better, or maybe it is as a result of the OLED screen as they ‘can’ use more power if it isn’t shown a black dot with the pixel turned off.
My iPad is at 257 cycles and 88% battery health.