We house ours in tubs for the first year or two, gradually increasing the size as they grow. Right now they're housed in 6qt tubs with lots of perches, but they can be moved into something larger after a few months.

They're like any other snake in that if the cage/tub is too big, they'll fail to become strong feeders due to stress. The container should be tall enough so that the perch is off the ground at a height that allows the snake to coil a meal up underneath it without hitting the ground (this sometimes makes them drop their meal). Be careful though about not making it too high so that the snake can't get down to the ground and back up!

As adults, 2x2x2 foot cage is good, but larger is better if you can manage. They'll usually use the highest available perch regardless of temp, so a horizontal heat gradient is better than a vertical one. We use back heat on our tubs since they're off the ground anyway, but a radiant heat panel is more appropriate for an adult-sized cage as it can safely be put inside the cage with the snake (unlike flexwatt, a UTH, or light bulb).