When configuring a maintenance window for a particular App the corresponding tile should be disabled when the start time for the maintenance window is reached. However, this doesn't work unless the user explicitly refreshes the Workspace portal. If the portal is not refreshed the user will still be able to launch the App, although it should be in maintenance. 

The same applies when the maintenance window has expired. if the tile is shown as "disabled" the user needs to refresh the Workspace portal to re-enable the tile.