I wouldn't marry anyone without shacking up first. But that's what is best for me. What is best for you could be completely different.
Chris and I dated long distance- me in NC and him in Missouri- for 2 years. We wanted to be together, but it seemed stupid to say "okay, we've been spending one weekend a month together for two years so let's get married." That seemed naive. But, I'm not one of those "gotta get married girls". The idea of marriage never entered my mind at your age.

It's all hard work. I say give yourselves every single advantage possible- whatever those are for you.

Good luck and congratulations.