Ever have to replace wheels?

No. Wow. 

I had one set that was on a box car. Had it since I was about 6 years old and  two wheels actually started to chip

Not on the home layout but, on our club layout we have.

Our club layout is located in the HobbyTown in Kennesaw, GA.  When we aren't there running trains ourselves, we have it wired so that customers of the store can push a button and run one of four trains on four loops. 

The trains we leave on the tracks for the customers get so much run time that after a period of time, you could shave using the wheel flanges.  We suspect this is caused by the Atlas track we used on the layout.  Our club "train doctor" has probably replaced wheels on the engines at least 3 or 4 times since the layout was built.

Curt

I had some MPC Geep power trucks that were used to the point where the gears that are cast onto the backs of the drive wheels were worn to sharp points. Those wheels were replaced.

Indeed, flat top "prototypical" track is much harder on wheels.

 

Lionel has stated that part of the reason that their track is "rounded" is to reduce wheel wear.