In talking with Craig, he said it is more dependant on climate change than time. If you live in the desert where it never rains and is low humidity, he said you could retorque annually. If you live in the Northeast with high humidity and rain during the summer and cooler, less humid winters, you would retorque more frequently.
I live in the Sacramento area and I retorque in the Fall once the rains have started and then again in late Spring when the rains have stopped and is low humidity and no rain all Summer long.
Jon Dembs