Added details on MGDC app consent expiry

Author: sannaga7

concepts/app-authorization.md

@@ -59,6 +59,8 @@ For details about how authorization works with different scopes, see [Authorizat
 
 Finally, the wizard confirms some key information on the app for you to review. You can select **Approve**, **Decline**, or **Cancel**. An action on an app is all or nothing. Authorizing an app means you're authorizing all access specified in the previous steps.
 
+An approval is valid until 180 days after the time of approval, after which the approval will be considered **Expired**. To renew an approval, an admin may revisit the application's approval in the M365 admin center, go through the application's details and  **Approve** the authorization for another 180 days. Similarly, to revoke an approval, an admin can access the application's approval in the same way and **Decline** the authorization. 
+
 When authorizing an app, you might encounter these error messages:
 
 - `App approver and owner cannot be the same user.`