The session timeout is enforced on each request -- not at the instant that the session would normally time out.  Whenever FoxWeb receives a request, it looks for a session cookie and if it finds one, it looks for the corresponding record in the session table.  If the last request for this session was made longer than Session.Timeout minutes ago, then FoxWeb considers the session expired and does not use the previously created session variables.

 

As you can see, nothing really happens at the exact moment that the session times out.  On the other hand, FoxWeb cleans up session variables once sessions expire, by simply reusing the associated session records.  If all you need to clean up is session variables, then you are covered.