I try to close the realtime document properly when the user closes the browser window. But nevertheless the collaborators that closed the document still appear in the realtime model. For how long will disconnected sessions remain in the realtime model until they get cleaned up? I've some of them in there for several days.
We recently pushed an update that should fix this issue. Collaborators should go away immediately if the page is closed normally and within 15 minutes in the event of a network failure or browser crash.