I thought that when someone is no longer in a job requiring clearance, they immediately get their clearances revoked.
I certainly did. A last debriefing, a signature, a reminder that releasing anything covered under it before a stipulated period of years and I'd go go prison, a plaque for the wall, a handshake, and an escort to the entry. People such as Brennan occasionally get an extension to cover ongoing operations, but nobody gets one as a souvenir.
That is exactly right. No Clearance of any degree once the job is finished for that individual. This has been a serious oversight and, in my opinion, has allowed treasonous people like Jarrett egress into areas she should not have seen at all and certainly not since Obummer was in office.