For what it's worth, I ran an MTH bump and go car on an O27 rectangle around my workplace's Christmas tree for 10 hours a day, 5 days a week between Thanksgiving and Christmas. Went for two years straight with regular oiling before the motor finally called it a day. In that time, I had to replace the roller pickup once. I calculated at the time that the little indefinite was running the equivalent of 13 actual miles over one 10 hour shift...
Mitch