I keep it on low power mode all the time. It will go all day and then some, but I am not on it for much. Checking Nostr over lunch etc. But I've had no issues with background processes getting shut down. Very pleased with the battery, and of course the security and privacy of the OS.

GrapheneOS is just polished enough to get the necessary things done but not so polished that you end up wasting time on distractions.