[kh99]

You could do this:

if (is_member_of($vbulletin->userinfo, 5, 6, 7, 10, 11, 109) OR in_array($GLOBALS[forumid], array(1, 2, 3)))
{
    $vbulletin->options['edittimelimit'] = '0';
}

This will change the edit limit for everyone in forums 1, 2, and 3. If you wanted the limit changed only for certain usergroups in certain forums, then you'd change OR to AND.