[Andreas]

@tamarian
I think you can achieve the same effect without a file modification and fix the next newest/oldest/last post problem using existing hooks:

Hook: fetch_threadinfo

PHP Code:

if (THIS_SCRIPT == 'showthread' AND $threadcache["$threadid"]['replycount'] > 555)
{
    $vbulletin->options['allowthreadedmode'] = false;
}