if your ESC has cutoff set at 6 Volts (3.0V per cell)
and you drive until cutoff in practice or bashing then you should balance charge every time.

If your ESc has setting for 3.2 or 3.4 volts per cell cuttoff then this is better and maybe not needed to balance every time.

As i have noticed taking them lower to say 6.0Volts for a 2 cell pack seems to unbalence them more dramatically. well with my intellect IP3800's anyway.

I measured each cells voltage at random times to find this info out.

Cheers