Only thing I can think about that might lower absorption rate over time would be scar tissue. I've heard the argument many times that androgen receptors do not down regulate ever, but all of that stuff is over my head.
there is no "down regulation".
androgen receptors are destroyed/created all the time.
there is no set amount of androgen receptors. the turnover actualyl depends on AAS (and other factors).
androgen receptor count and half life actually INCREASES the more AAS you use. there are studies on that.
@OP
you will have to use more simply because youll be bigger and not lose as much mass in between cycles.