In my experience, with a recently flashed Mobian on a UBPorts CE Pinephone, the phone can sometimes last 24 hours on idle (no SIM card, Bluetooth off, WiFi on). The problem is that Mobian often ends up in a cycle where it wakes the phone (including turning the screen on) for several minutes at a time for what seems like absolutely no reason. Leave it on a table while watching a movie and you'll see it light up and show the login screen for many minutes at a time, go back to sleep and then just a few minutes later wake up again. This bug has existed for many months now and can reduce standby battery time to only perhaps 3-5 hours.
Maybe this can also in part explain the wildly differing battery times that people report?
Maybe this can also in part explain the wildly differing battery times that people report?