Since the motor deterioration can be kind of technical, you might post this as well at endless sphere. Heat will definitely kill your motor faster, so that's one consideration; how well does your current motor dissipate the heat? It may be wise for you to learn from the endless sphere folks how to take apart and rebuild your motor, considering the stress/usage you put it through. Since it's your car, it might be worth the investment in the necessary tools if you don't want to pay someone to service it regularly.