Hubs rooms stay open until you "close" them. You will always be able to use the room URL to visit your room until you "close" it. If you plan to revisit a room, you might like to add it to your favorites for easy access.
To close a room:
Click on 
in the bottom right corner, and select . When you close a Hubs room, links and codes to the room will no longer work for anyone, including the room owner.
