I myself, have only calibrated my AC once when first activating and first flight. The manual suggests only doing a calibration if prompted to do so.
You should when you boot up, check your sensor states, the IMU and the compasses, making sure they are happy and in the green, and rechecking after lift off.
Oh, and stay away from all metal when booting/firing up your kit.
Side note, I'm up in Moraga, we should meet up sometime...