impossible to say. muscle growth and upkeep depends on a lot more than mere receptor stimulation - labile nutrient pools, other implications of screwing around with your hormone cascade etc etc
one school of thought would say that the time on = time off theory allows sufficient time for your body to return to a pre-roid state and therefore be primed for another cycle, but then again, you could argue that doing a 3 month cycle and staying off for 9 months allows for superior consolidation of gains.
its murky. common sense (looking at how roids have been used in the past and hte results you get) would suggest that you can get away with more than a cycle a year
cheers