Session Garbage Collection for expired logged in users

[eluser]Aleazus[/eluser]
I currently have no expire time for sessions. I set a session data array variable logged_in to simulate an expire time for logged-in sessions. Through the modified garbage collection it only deletes expired logged in users and null cart sessions. The only simple change I plan to make is to not destroy a logged in user's session if they have a cart, rather log them off. If you would post how you setup your session expiration functionality, that would be much appreciated and I would have a direct comparison.