Virtual Classrooms/Live Rooms close 5 minutes after the last user leaves the room. After those 5 minutes have elapsed, if a user (not an instructor) attempts to enter the room, he/she is given the "Instructor Offline" message. This "session time-out" does not apply to the instructor; he/she may re-enter the room freely at any time.
It is important to note that during those 5 minutes, the room remains open and users can still come into the room. If a new user enters the room before those 5 minutes have elapsed, the room is "re-engaged" and the "session time-out" is suspended. The room then remains open until 5 minutes after the last user joined the room.
Please see the article End Session to end a particular session instantly