Discover that small UPS batteries fail regularly, usually with cooked batteries.
Add maintenance routine for UPS battery.
Begin to wonder if this is really worth it when the rest of the house has no power during an outage.
Get small generator.
Discover that small generators also need maintenance and exercise.
Decide to get a whole house battery backup a-la Tesla Powerwall topped off by solar and a dedicated generator.
Spend 15 years paying this off while wondering if the payback was really worth it, because you can count on one hand the number of extended power outages in that time.
In the end times a roving band of thugs comes around and kills you and strips your house of valuable technology, leaving your homelab setup behind and - sadly - without power. Your dream of unlimited availability has all been for nought.
Conclusion: just replace the CMOS battery on a yearly basis during planned system downtime.