All good stuff, but if you understand how the instrument actually works you will also understand that when you "set" the card (realign the gyro) simply screwing the knob around to the "correct" position and letting go is not in itself enough.
You must hold (or push) the knob in the new position for sufficient time to allow the gyro to settle properly on its gimbals, resolve any acceleration errors and find its new position in relative space. You will find that it will be more accurate and the "precession" rate will be less.
