Currently have just over 65,000 miles on my '05 Chopper, BUT had the engine rebuilt at around 58,000. At about the 58K mark, I was burning oil A LOT, and had oil coming out of the air cleaner area. A broken valve guide finally sent a small piece to my oil pump, causing it to seize up.
So all and all, one could say that my rebuild was required due to something breaking in the engine... namely the valve giude. However, it also needed the cylinders bored, with new pistons installed, of which would certainly fall into the category of "wear".