Yes it is and the most important but that is a whole other subject.
It may be a different subject but the 2 go hand in hand. I think the reason why people are resorting to such large cycles is because smaller cycles didnt get them what they expected so the natural progression means more gear = more gains.
The truth however is if your not making excellent progress on low/mid dose cycle then you have something else holding you back and that something is nutrition.