Regardless of reaching your genetic natural maximized state, the human body has a pre-programmed natural homeostatic state that it will try to maintain. Exogenous AAS will infact shift this homeostatic state towards hypertrophy as desired (yes, possibly with all of the associated sides that accompany it). And just as expected, it will revert to its prior state as as much as possible once exogenous input is discontinued...(search a before/ after of Kevin Levrone, for example)
There is no time limit on reaching this natural limit. It is regulated as a function of metabolic nutritional input and the stresses we place on the body. Work = force X distance. Hypertrophy = work + adequate metabolic nutrition + repetition + genetics + (time/rest?). These are all variables in a grand equation of achieving your natural that will change the desired result with just the smallest of incremental variations.
Few, if any, athletes will be able to figure out this equation and maximize the results naturally without AAS. That's just the way it is.
You mention some time based goals. What are they? If you plan on making a career out of gaining these results in a short time, then the writing is on the wall, so to speak.