There is no hard and fast rule about how many "extra"miles you get. But every seal, moving part, and wearable component will wear out faster.
The reason you don't get a scientific answer is because that's just not possible.
The reason you don't get a scientific answer is because that's just not possible.
The difference between replacing a wearable component at 100,000 km or 101,000 doesn't make a huge difference (ignoring the fact that it could just fail earlier due to one of a hundred different environmental reasons)