I would only change it if a couple things did not fair out. First check the drop in the chain tensioner if it not below 16 mm then that bugger has hardly stretched at all. If this was true and you do not need any valve shim adjustment I would leave her alone. If you have to release the chain to shim her then I would change it and the cam chain guide on the tensioner side if you do not have the updated guide. I have seen guys go over 70,000 with no problems with the chain.. I have 60,000 on mine and its fine.