Expiring groups in Office 365 groups is a new Azure Active Directory Premium feature that is now in Public Preview. This message is associated with Office 365 Roadmap ID 14680.
How does this affect you?
You can now manage the lifecycle of Office 365 groups by setting expiration for any Office 365 groups that you select. Once this is set, owners will be asked to renew their group as they come close to expiration if they want to continue to use them. Any group that is not renewed will be deleted. Any Office 365 group that was deleted can be restored within 30 days by the group owners or the administrator. This feature is now available in public preview to all Azure Active Directory Premium customers.