Normally, a timing chain does not have a catastrophic failure like a belt breaking. It simply stretches over time (hours of running) until either the tensioner can't keep it tight or the crank to cam timing shifts enough to affect the performance of the motor. There should be no periodic replacement of the chain. I once replaced a timing chain on a Saab I owned that had 270,000 miles on it. The slack in the chain was causing the ignition timing to float causing rough idle. Nothing was actually broken but I replaced it to get the motor back to optimal running condition. I sold the car later with somewhere around 295,000 on the clock and the motor was still running like a fine timepiece.