I have been reading Bottomline Bodybuilding by Nelson, and from some of the things he has been elaborating on in his book about steroids and steroid cycles, he is being remarkably diplomatic in this one.
The whole thing with the body and homeostasis, there are quite a few theories floating around about the body having 'set points'.
For example, there is a huge amount of information about set points for bodyweight. Our body will try to return to a set weight it is used to.
This is one of the biggest issues with dieting, as so many people, in particular overweight women will diet for ages to drop their weight, but the diet is a temporary solution, not a way of eating for life.
When they come off the diet, the body wants to return to the previous set point.
It is thought that unless a lower weight is maintained for at least a year, this is pretty much inevitable.
Maintaining muscle, as it is even more metabollically demanding, is even more difficult to maintain IMHO.
Nelson has some very interesting, and in my opinion, really valid points for running much shorter cycles in his book.
I think the issue is not what you gain on a cycle, or how much more you will be suppressed, as it is quite obvious the longer you are on the more you will gain (if diet and training are good), and your body will be less used to producing its own testosterone, so you will be more suppressed.
The issue is what are you going to KEEP after you come off.
It is also harder to maintain your gains the longer you have been suppressed.
Just like dieting to STRIP the fat, you have to trick your body into lower body fat, you also have to trick your body into putting on muscle and keeping it.