When creating a portal, you can set an expiration date, and when that date hits, the portal is no longer accessible to anyone with a link to it. When accessing expired portals, users will receive a messaging stating that the portal is not active.
Expire a portal from Options > Share on the portals dashboard. Expire it on a future date or the current date, or clear the expiration date if one isn't needed.
Expired portals can be updated and edited by portal creators from the Portals dashboard, but can't be viewed until the expiration date is changed or cleared. If the expiration date is cleared, the portal will display again.
An expiration date is not required.