i would suggest a different approach on this hack, as it's using a template for nothing:
simplier, but as efficient:
PHP Code:
/////////////////////////// step 1 ///////////////////////////
/*
Add new Phrase:
Type : Front-End Errors
Varname : zzzz_oldthread
Text: This thread is old. Consider starting a <a href="newthread.php?$session[sessionurl]do=newthread&f=$foruminfo[forumid]">new thread</a> instead.
*/
/////////////////////////// step 2 ///////////////////////////
//In forum/newreply.php at about line 108 find:
// ### CHECK IF ALLOWED TO POST ###
//And afterwards add the following:
if ($threadinfo['lastpost'] < TIMENOW - 2592000) // 30 days in seconds
{
eval(print_standard_error('zzzz_oldthread'));
}