Well, the bad news first - during upgrades today there were a few hours of unplanned downtime. The issue was unknown until after a reboot had been done, and was harmless apart from a failed boot (no data loss, in other words). An LVM2 LV had been decommissioned and removed more than a month ago but I had forgotten to remove it from fstab. Easy fix, if a bit embarrassing on the oversight of it.
On to the good news: As part of this I’d planned to double the RAM for Centre. I noticed that it was quite frequently using up most of the 9GB of RAM assigned to it, so I upgraded that to 16GB. It’s now more responsive and a little quicker.