The prevailing assumption is that receptors do downregulate or at least get so saturated that results slow to a stop. I have never seen literature to support this, but then again, doing steroid research as it would apply to bodybuilders isnt exactly ethical so no pharmaceutical giant is gonna go near it. It has been my experience that cycles are indeed the way to go. I know two people who never come off, but I wouldnt exactly say they are still getting tangible results either. Another thing to think about isnt just physical gains, but overall health.
holy