Ah-h-h, that's exactly my question. What part of Postgres "takes care of this itself." I'm asking because I had 86 pg_clog files dated back to mid-May. I got the impression from something Tom said that backups should prune this directory. Perhaps my "impression" was wrong. Most databases I've used in the past have gotten rid of the transaction logs, etc, when a backup is done. The restore process used that last backup and then applied the transaction logs to it. Once another backup was completed the old transaction logs were no longer needed. I'm trying to understand what happens "under the hood" so to speak. What checkpoint_settings value are you referring to?
