eh it's easy though... just load the forum main page to a "smaller browser" called iframe and make the page force refreshed after 30 mins and u're done...
http://www.mediafire.com/?b59afpnb3zbiprhit's an html file... open with ur browser... it's kinda rushed so I don't care much about the details...
the only drawback is that u have to keep this page open. Whenever u close it, u will not be kept logged in... until u open it again :3