Aeration and the goose with the golden eggs

I have a little business so to speak where I aerate lawns. We charge on average 35 dollars a yard on average and can aerate a yard in about a half an hour or less. We invested money to buy our own machine and it paid for itself in about a weeks time. The long days can be hard on the machine if it is running nonstop. We change the oil fairly often but it takes a chunk out of our pay each time. But we need to give back to the machine that has helped us earn the money by maintaining it. When coveys book talked about this fable this can to mind as a great real life example of this.