You'll only need more than 1 pack if your racing at a club with very low numbers and quick rounds of racing!
I've had 1 pack for each of my cars for the last 5 years, running at the front end of the A finals at my local clubs with 4-5 heats of cars running, so little more than 30 mins between races, topping up as much as time allows in between and have no issues
Half decent lipos don't drop (noticeably) in performance over 5 mins, though over a year or two of regular use they do slowly degrade....but only very very slowly!
You could probably get 2 runs out if a pack without charging, but no more than that without risking them dumping during a 3rd run...which isn't dangerous as long as your ESC has it's lipo cutoff set correctly.
I balance charge before each run myself though, as do most people.
Enjoy the new bread of electrics
