No it doesn't work like that, statistics etc. As with any fixed interval maintenance part there is some chance that the part can fail before being serviced. As

No it doesn't work like that, statistics etc. As with any fixed interval maintenance part there is some chance that the part can fail before being serviced. As per my example, the timing belt was replaced at 100k, so the new belt failed at 60k, just bad luck. Fixed interval maintenance is used for parts with a tight normal distribution when failure occurs and where you can't predict the failure before hand, or it is difficult to measure / predict. Timing belts fits this use case.