@lunarised @pwm @iwillbite what command are you using? The pleroma prune process can be more or less aggressive depending on the arguments.
This is what I use, monthly:
./bin/pleroma_ctl database prune_objects --keep-threads --keep-non-public --prune-orphaned-activitiesBasically keep things that are part of threads I was in, and keep DM/private threads, but dispose of anything else.
Of course, I only have me and the bot for active users, I dunno how many others you have.