Under Admin -> Settings -> Files there are these
clean up uploads [default: enabled]
Remove orphan unreferenced uploads to prevent illegal hosting. WARNING: you may want to back up of your /uploads directory before enabling this setting.
clean orphan uploads grace period hours [default: 48]
Grace period (in hours) before an orphan upload is removed.
purge deleted uploads grace period days [default: 30]
Grace period (in days) before a deleted upload is erased.
It might be that making an upload an orphan would result it it being deleted. I haven’t tested, but AFAIK these settings do not clean up older posts retroactively.
One problem I see here is defining “old/irrelevant”
- Admin judgement call?
- last post date?
- last viewed date?
- topic status (eg. Closed/Archived/Unlisted/Deleted)?