All Apple cables seem to have a weakness where the cable joins to the connector. A short PVC tube is no match for a gradually tapered part found on some Ethernet cables. And the fact that the user usually just yanks the cable instead of pulling on a tiny connector part...
Obviously they won't be last indefinitely, especially for a connector used as much as a power input. And I have no idea if all the connectors follow properly the standard regarding materials.
But given the built quality of Apple cables, I doubt we will see the device connector wear before the cable is ripped apart by natural degradation, after 1 or 2 years.
I have a new electric kettle with a plug that incorporates a ring into the strain relief -- your fingers will always grab the ring to pull it out of the outlet, and that's where the cable-to-plug connection is strongest.