Workspaces can be set to automatically archive and delete on a specified date in the future. To do this, you need to be an admin user in the workspace.
Go to 'my workspaces' in the action menu.
Find the workspace you wish to archive
Click on the three dot menu on the right side of the workspace
Choose 'Schedule workspace archival'
Select a date in the future when you want the workspace to archive
Choose the recipients of reminder emails
Selecting the 'Delete workspace after archiving it' will permanently delete the content after archival. This is not reversible and should not be done unless you are certain nothing from the workspace is needed any more.