You can set some limitations like 3 motors total, and only two sets of tires allowed, letting it be part of the team's strategy to sacrifice lap time for the time it takes to get fresher parts.
thats not an endurance race.
as for the second car thing thats the other tim's idea but I went with it because its all for fun. If your dumb to break your car just to use a fresh car then more power to you. If it was more than a hour race then you should have to fix your car but if you break a part now by the time you get it fixed you would be like 5,10 15 mins down and where would the fun be.