If you were to dump a 4900mah pack in 6 minutes, you would be pulling 49 amps average.
On average I put about 1500mah in 2wd and 2200mah in 4wd back into my nimh's after a run, so thats 15amps and 22amps average consumption assuming the car is running for 6 minutes (warm-up lap ect).
Saying that though the cars must pull significantly higher currents when accelerating hard, as I borrowed 3200 and 4900 (not sure of the C rating of each pack, but the 4900 was higher) lipo's from Jimmy at Southport recently and the 4900 had a lot more punch - even in a 2wd with a 7.5.
As for them overheating, I wouldn't worry about it
