Agreed that's a weakness of my approach.

Jason Flatt wrote: 
On Thursday May 3 2007 10:23 am, Haisam K. Ido wrote:
  
uid=$uid

$sql = "SELECT node.uid,watchdog.timestamp, node.changed FROM
`watchdog`,node where watchdog.message like \'Session closed for%\' AND
node.changed >= watchdog.timestamp and node.uid=watchdog.uid and
node.uid=$uid";

I believe that the above query returns all nodes which have changed
since $uid's last login.

    

So I guess you have your site configured to never delete any log entries?

admin/settings/error-reporting