How about enabling and starting the timer service only if /etc/systemd/system/$SERVICE.timer.d/schedule.conf does not match the $PERIOD in /etc/sysconfig/btrfsmaintenance? Would that solve the issue? We will still have to check "systemctl is-enabled $SERVICE.timer" and "systemctl is-active $SERVICE.timer" and enable/start iff it returns false. Would that slow down the boot process?