Yeah, that's a fascinating technical question if someone were to try for a "car for life" model. My college car was still driving fine when I sold it (at about 13 years in its life and something less that 70k miles), but the interior plastics were deteriorating faster than I would have expected to the point where pliers were needed to be used to adjust the a/c as the knobs broke off and probably the window cranks were about to follow.

The other side of it too is accidents are likely to always be an issue with cars (even in a world of self-driving cars, I suspect), and there are plenty of other safety reasons cars shouldn't be expected to be driven for too many years without replacement.