This one isn’t really HA’s fault, but I think it would be nice if there was a way to manually enter in the expected amount of time in between charges for a device and a way to reset that value when a device is charged. At this point I’ve got >30 different battery powered devices that are connected to HA in some form or fashion, and while I’m sure there is a way to configure the reminders how I want them, it seems like it should be something that is easy because it is a problem everyone has.
Bonus points if the expected battery life could be updated based on previous length between charges.