The truth is, the body doesn't really downregulate androgen receptors the way it might with recreational drugs
In fact, there's evidence of slight receptor upregulation.
THe reason you can't keep growing on the same doses is not that your body has accustomed to them, it's that you're carrying an increasingly unnatural level of inflated muscle mass, that requires steroids to maintain.
so steroid effectiveness is related to absolute muscle mass, not length of time using them. for instance, if you blew up on a bunch of cycles and then stopped and shrank down to your natural weight, and then decided to resume use, they would be just as effective as they had originally (if not more effective b/c of muscle memory)