Will repeated usage of the usb C port wear it out, or cause damage in Mac?

With the 2016 & 2017 USB-C Macs, yes.....the USB-C port will easily wear out since the very fragile fiberglass board is used to help hold the USB-C cable connector in place. Apple added a metal reinforcement to the edges of the USB-C ports with the 2018+ models so they should hold up much better.

Eventually... but I have never heard of a single case in which that has happened.

Considering the billions of Apple devices in use worldwide, if it were a problem I think we would have heard about it by now.