I'm a very young man seriously contemplating a vasectomy. Any advice?

Um, dude you will most likely seriously regret getting a vasectomy. And off course you haven't had a yearning to have a family or children - you're 18 years old! They're not always reversible as you said. If you do find a girl that you particularly like, and she wants to have kids naturally (cuz some of them care about that for some reason), and you can't get it reversed, you are f***ed!