How to change cache lifetime for a specific feed

function tifd_feedzy_cache_duration( $feedCacheDuration, $feedURL ) {
    if( 'http://themeisle.com/feed' == $feedURL )
        return 60*5; //5 minutes
    return $feedCacheDuration;
}
add_filter( 'wp_feed_cache_transient_lifetime', 'tifd_feedzy_cache_duration', 10, 2 );