Tex has something there - turnaround time is long with a big pack that is 'buried' in the model. Even if you fly so it stays cool, put a blower on it post flight and start to charge immediately, you'll still be looking at nearly an hour turnround on a 30+ cell battery. My 1/5th Cub is starting with 20 cells - two handy 10 x 2000 mA nimh packs I already own - though it probably only needs around 16.
Big "However" - I have other models with multiple & fast swappable packs to fly inbetween, plus I don't see the Cub as a model to fly all that much.
So, flying the Cub, putting a cooling fan in the cockpit for a while to cool off the nimh and a slow recharge is no real issue to me.
Am already beginning to wish that I'd built my 1/5th like one of those 200HP clipwing monsters! I have a hard time going around in lazy circles for overly long