Couple of points that I started to make but neglected to finish.

Every now and then I'll do a manual purge where I'll filter only on "unflagged" photos and delete them from the disk and catalog.

With my recent hard drive failure, I've often wondered over the years whether its really worth having raid. And this single event has dispelled any doubt I've had. Yes, all my data is backed up, so there's very little, if any, that I would've lost. But despite the cost of buying 4 new 12TB disks (yes, I could've got away with replacing just the one) and the time it took to rebuild (almost a week, as I added the disks one at a time, and rebuild the entire array each time), it was still a lot less painful that restoring everything from backup.

You're absolutely right. The correct way to handle this would have been not to wait for a disk to fail and then suddenly find yourself with all old disks after 12 years. Instead, it would be to replace just one disk at a time every 2-3 years, depending on its operating hours.

Have you ever tried cataloging videos with Lightroom?