E = IR
Its a very true formula... if you re-arrange it, you'll find that current and voltage go hand in hand (if one increases, the other will too).
R = E/I
Basicly, if you increase the voltage, you'll increase current draw, and thus stress the motor and ESC more. If i were to run a higher voltage, i would drive smoothly. punching the throttle will blacken the comm, and wear the motor out faster.
Hope that helps! Cheers!