Holden Astra 2001: When should the timing chain be replaced?

IT'S CERTAINLY early, very early. I would suspect the chain lost tension for some reason. Was the tensioner changed at the same time that the chain was replaced? Chains are used by carmakers because they last longer than belts. Over time they wear and stretch and ultimately become noisier, but I wouldn't be expecting to replace a timing chain before 200,000km.