I go through some settings on the Zoom F4 in the above video and discuss how to get extra time on set through saving battery. The method may be slightly different but can also apply to the Zoom F8.
The key themes are:
Set your phantom power to 24 volts if your microphone is compatible.
Set the zoom to stop phantom power when playing back audio files.
Just turn off the phantom power during long breaks resets etc.
Lower the brightness of the LEDs and screen if you want.
And look after your batteries, keep them in a plastic case it extends their lifespan in general and they wont discharge as much during transit.