You've got several really subjective questions in this question. Will you be able to make gains by running test for a long period of time. Yes. Will the gains taper off, unless you change dosage/type of gear? Yes. Will the gains be keepable when you come off? Many factors determine this, not just what you do while "on" cycle. I have a feeling this thread is going to get some back-and-forth feedback about what is a good idea to run and for how long, but in my opinion, running shorter cycles and not shutting yourself down is better for keeping gains and your health. The longer and farther you go from your bodies "natural" ability, the harder it is going to be to sustain when you go back to "normal."