We all take calculated risks in anything we do but by not coming off, your chance of risks goes up higher. If you have the genetics to turn pro, you won't need to stay on year round at 20 years old. Further, you have to understand that the number of people that actually go pro and make a living at it are a very small %. Most everyone who competes will never make it to that level, no matter how much they sacrifice. Your sacrifice may be great. At your age, your body is still developing. Your natural hormones would be at their all time highest. As it is, there is going to be a very high chance that you may find that you NEED HRT for LIFE, by the time you're 25 yrs old. You may suffer from ED and not be able to have children. These are pretty big sacrifices to make for someone your age, especailly considering the chance of turning pro isn't going to be that much greater than if you cycled on and off. 

Hopefully, you are seeing a Dr and getting your labs done about every 3 months. Its important to understand whats going on with your body. Gear isn't only going to effect your sexual health. It can impact all of your organs and it's important to make sure that everything is still working properly. Even guys running low doses can suffer from major kidney damage and elevated liver values. Your heart can enlarge over time. If you are seen every 3 months, whether cycling on and off or staying on year round, you will be able to maintain your health. If you are not doing this, then I can tell you that you are not responsible enough to make such a big decission as staying on for life.