While you’re right that going all the way up to the 4.2v that the battery is rated for is worse than if it just stayed at 4v, by not discharging to half or more you’re reducing the charge cycles which directly correlates to longer life.

Ultimately in lieu of a charge controller or os that does that for you, the easiest way for a user to extend battery life without going psycho mode is to charge they phone, eat hot chip and lie.

I know all the macs and iphones have that predictive charging thing where if you’re always leaving your phone or computer or phone plugged in overnight they’ll keep it around 80% or so till about an hour before you wake up and charge the rest of the way then.

Windows computers have something called smart charging but I don’t have any experience with it.

Theres a bunch of different ways to control charging in Linux.

It really seems like this is a solved problem and I’m glad to not be worrying about plugging and unplugging my phone to maximize my battery life.