One thing I have noticed is you wont use nearly the same amount of mah in the same 4-5 min race as you use to, also you no longer have to discharge them all the way down prior to charging them again, and you dont have to sit there and wait for them to cool down normally as they normally come out of the car at room temp lol.

I know a guy who races with one pack. He pulls it out of the car after his heat, pops it on the charger at 8amps (make sure the pack can handle that much prior to charging that high) and then goes out to marshal. Says he has never had an issue as long as there were 4 total classes racing that night.