Volkswagen's original timing belt intervals were designed to accommodate all markets, but since then they have changed the advice for markets that are not considered harsh environments to 160,000 miles or more, effectively a 'lifetime' belt. Volkswagen believe that the quality of the components allow for this interval, but it is up to the individual owner as to whether they are happy to accept this advice or not. We would suggest having it changed earlier than this if you intend to keep the vehicle long term.