On Google's Workspace updates blog, they recently announced the general availability of group membership expiration.
From their site:
"The Cloud Identity Groups API feature that enables you to set expirations for group memberships is now generally available.
This enables admins to set an amount of time that users and service accounts are members of a group. Once the specified time has passed, users will be removed from the group automatically. Automatic membership expiration can help reduce the administrative overhead for managing groups, and can help ensure group membership is limited to the members that need access."
I thought this could be a useful feature and bears further discussion.