Any reboot means service interruption. Any reboot has the potential that your system fails to return to a proper working state. There’s gazillions of things that can go wrong on a restart and the least thing you will want is that it happens when you’re not there on standby to fix problems right when they show up.
Proactive restarting is 80’s or at best 90’s thinking and a real No-Go in modern system design.
Companies to operate internet services would never ever think of proactively (needless) rebooting their servers. There is a lot of wisdom in the saying “never touch a running system”.
Availability isn’t about HW reliability any more. It’s all software design. If services fail today it’s software 99+% of the time. Yes HW can break so you need to prepare and have a spare ready, but companies don’t use $5k servers because they’re more reliable than a $50 SBC.
The only reason they pay a premium for HW redundancy like dual power supplies is that the server is located in some remote datacenter and that it’s more expensive to repair it even if that’s only needed once in some years.
openHAB is designed to run 24/7 and openHABian is designed for system availability.
The SD mirroring feature is built the way it is because it even allows you to talk some layman like a family member or neighbour of your summer cottage through a replacement process from remote.
You cannot because no SD vendor tells and even changes without notice. It’s an irrelevant side branch leading away from the main points anyway. For the whole story see Corrupt FileSystems every 2-3 month? - Setup, Configuration and Use / Beginners - openHAB Community