Thats why tires have a date on them. At 5 years old they break down just by sitting in the warehouse. So a belt spinning around at high RPMs and in the heat under an engine is even more likely to fail. Sure you may get 200,000 miles out of it but there are a lot of VX engines out there that failed and not all from oil. As far as not broke dont fix do you wait till a tire blows before you replace it?