Guest Users - Clean Up

+1 on this question. The 'get-azureaduser -filter "usertype eq 'guest'" doesn't show too much that might lend itself to expiration and the like. I'm looking for the same thing. The closest thing I've come up with is something I did in our on-prem AD to handle expiring accts. At time of guest user creation I include the requestor's objectID and populate it in the 'manager' field. I want to cut a report off of that which will email the requestor at regular intervals (i.e. quarterly, or some kind of 90-days from creation date). While not elegant, it at least gives us a means of tracking and managing.
Any assistance is appreciated.