The reality is even more nuanced. The reality is that you gain less muscle tissue on a blast than you think, and much of the visual affects are due to water entering muscle tissue (due to higher test levels), or some other cosmetic affect from tren, DHTs, etc that makes you look a certain way. When the blast is done and you go to either TRT or natty, these water gains and cosmetic affects go away, and all your left with is the gained tissue. Your body can hold on to some of it due to more proliferated myonuclei and if you’re technically not at your genetic limit, but you’re still going to lose tissue in the months to come while back on your natty test production (which will be less than before for a while), especially if you had put much of that tissue on with tren or a 19-nor. ****Ultimately, the muscle tissue you keep months after your PCT, even if it’s more than what you could do natty over a longer time span, will absolutely pale in comparison to how you look while you’re on the blast.****
And this is why it is NEVER “just one cycle” where you go back to training natty and live happily ever after. The true “just one cycle” all quit the gym entirely because lifting natty seemed entirely pointless, and they didn’t care about juicing anymore. But in all likelihood, if you’re the kind of person to take steroids in the first place, you’re the kind of person to keep on taking steroids, and (hopefully) do whatever it takes to mitigate health issues while you continue to make gains
With all that, please think hard before pinning yourself for the first time. It truly will never be the same afterward, and you need to be prepared for the high possibility of lifetime dependence on at least TRT, both physiological and psychological. In truth, at your age, I don’t know if it’s possible for you to be prepared for this