One reason I read recently about former intel people keeping their clearance has to do with the obvious insight and information they could provide if needed in case of an emergency or simply as overlap in knowledge for ongoing investigations. Those former intel people wouldn't have to undergo the (now slow) security clearance process to be brought up to speed with issues that may have knowledge on if need be (even though they carry a 'former' in their title). It only doesn't make sense if you subscribe to the idea that all intel is partisan.