well i have about 8 different databases,
1 is for Archives, than i try not to feel all the others divided by customers, but it happened to me that optimizing databases at the same time brought me into a downtime and all databases unreachable for 5to 10min.
very strange i must agree. there was something wrong with one of the database and optimizing in the middle of the day is probably not the most recommended, something wrong with systemd timers, i switched to cron
problem got solved after that and i pushed the daily optimize script to the middle of the night but still i'm still wondering if the new versions of postgresql would improve stability and performances or just bring absolute incompatibility and mess.
I would love to try myself but i got lazy on those tests lately... :/