I was wondering if MS could introduce a feature where in Distribution List/Security Groups or any other modern groups would have option to renew yearly. DL's some time grow rapidly that become very cumbersome job to cleanup. As soon as DL nears expiry an automated mail should be sent to Owner asking if DL needs to be renewed? if not then DL will be expired.
This would be easy to code with PowerShell. Look for distribution groups whose WhenChanged attribute is more than a year old and send a note to the group managers asking them if they want to keep it... etc. etc.
There is a script I found a while back that searched message tracking logs and compared that to a full group listing. Used that to see if a group had been used, and if it had not the group was disabled/removed.
While the feature is not built into Exchange it is something that can be scripted and run on a schedule.