Might also make sense to, if not delete them, mark them as old and move them to a different storage location/server. Would enable them to be put on, say a spinner, or on a lower-powered server with spinners.
Good call. I'm about to look at methodologies now, first I'm posting a Community Seeder for new or small instances here momentarily. The purgePost API could work, but I'm going to need direct DB access to get a list of saved and commented on items for all users anyway, so this may be deeper. I'm