There are 2 settings on the FileDirector server that could affect this:-
1)...In the Config Utility (Server), on the tab Server, there is a Session Timeout (in minutes) which is the "period of inactivity after which a user’s FileDirector licence will be made available for other users". This setting will affect all users, WinClient and Web Client.
2)...In the Internet Information Services Manager, under the server name node select Application Pools. Right click on the name of the FD web application pool (usually FileDirectorWeb) and choose Advanced Settings. In the Process Model section there is a setting Idle Time-Out (minutes). This setting affects all web applications that use that application pool.
Please let me know if you require any further information.