I will have to add a checkbox (and maybe a number of hours between syncs box) or something to enable a scheduled sync. Even if the write amplication is low, I still don't want it running on my systems that have a UPS
Agreed. I would make the default an 4 hour interval and setting to 0 disables it. No idea whether current installation should be 'upgraded' wrt this default or users need to know about to enable this feature after a future update...
Wrt amount of data to be written: when we started with this approach in Armbian we had the same concerns and came up with rsync, keeping old logs on storage and trying to reduce writes as much as possible. Still not to our satisfaction since currently there's an issue with logrotate. But too exhausted currently to look into... I'll drop you a note once we improved the situation.