Right now a session will be removed if the agent is unresponsive for more than 30 minutes. In most cases this is more than enough, but it does occasionally happen that there are network issues longer than this. We've had several requests to alter this behaviour so that the user can reach their session again once the network issues are fixed. Another reason for reconsidering this is that the stray sessions that have been abandoned can also cause problems, forcing the administrator to manually go in and terminate them. Also see bug 5476 which concerns how we interact with the client whilst the agent is unreachable.
This behaviour was fixed on bug 5476. *** This bug has been marked as a duplicate of bug 5476 ***