Depends on how much you brake, and how much traction there is.

On slick dusty tracks I never get up to speed enough to need brakes, just toss the car in and dial it so it deosn't traction roll but slides and drifts well. Battery lasts forever on those.

1 hour on my 2000mah Protek is cake. 2hrs is just plain pushing it. But I'd bet money on 1.5hrs being safe at my track.