Parts do where out, even well maintained ones. its hard to judge just how many miles a car can go because if you replace parts, and maintain it well. then it 'should' last forever. mounts will wear out... they use rubber in their construction. pistons in an engine wear over time as thats metal slapping against metal. even though they are lubricated by oil, they do wear. you replace tires, belts, etc etc because they wear. well ALL the parts in your car will eventually. just some take longer than others. the maintaining only actually prolongs the actual usage of the part. so, good maintenance = a long lasting part(s).