If your goal is to cache the output of the template, use fetch() to store the output in a variable, then cache that variable using something like Cache_Lite. Psuedocode:

// build $cache (Cache_Lite instance)
if (!($html = $cache->get($cacheId))) {
// require Savant
// build $tpl (Savant instance)
// assign $tpl vars
$html = $tpl->fetch();
$cache->save($html);
}
echo $html;