RSS <ttl> Element

<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0">

<channel>
  <title>w3ii Home Page</title>
  <link>http://www.w3ii.com</link>
  <description>Free web building tutorials</description>
   <ttl>60</ttl>
  <item>
    <title>RSS Tutorial</title>
    <link>http://www.w3ii.com/xml/xml_rss.html</link>
    <description>New RSS tutorial on w3ii</description>
  </item>
</channel>

</rss>