Show the expiration date of the CMG certificate
When you open the properties of CMG, the expiration date of the CMG certificate should be shown.
And there should be a console notification if the expiration of the certificate is in less than 7 days.
This is a good idea but I'd suggest making the notification 30 days instead of 7 just in case someone isn't available within a short time to assist the ConfigMgr admin with certs.
It would also be a good idea to add this to Management Insights.