Starting in a directory on my server, I need to delete all directories below it which only contain files older than a certain age.
To be clear, I don't just want to delete old files; if a directory has any new files in it then I don't want to delete the older files that might also be in there.
Background: I run dspam on a server, and it creates a directory for each mail address it scans, containing a log and a quarantine mailbox, amongst other things. I have many many directories that were created automatically for non-existent users and haven't seen any changes in months or even years, but "active" directories do have old files in them (preferences files, etc). So I want to find directories that haven't had any of their contents change in (say) 6 months, and then delete the whole directory.