This could be problematic if the same user is logged in from multiple machines. Logging out from one client will invalidate all of the other sessions. For some web applications this would be seen as a bad experience to the user.
Another issue is old sessions may be deactivated once the user logs out, but all those old sessions suddenly become valid again when the user logs in again, since the time stamp field is now present. It doesn't prevent the issue the author is highlighting (that sessions can last forever).
Another issue is old sessions may be deactivated once the user logs out, but all those old sessions suddenly become valid again when the user logs in again, since the time stamp field is now present. It doesn't prevent the issue the author is highlighting (that sessions can last forever).