> I don't really see a point in checking the login time of the user with
> some cron job. If he wants to leave a page open for 2 hours that's fine,
The session is normally expired than

> he can't do anything special with it. If he closes the browser the
> session is destroyed,
No, it's not. There is no sure way for the server to determine if the
browser is closed. The session will continue to exist until it expires.
Only the browser will forget how to access it.