In a slightly different situation, my older sister met her (now husband) during grad school and the majority of their relationship was long distance. She was in medical school, he was at West Point. Right before he was deployed to Iraq he asked her to marry him. He came back a year later and they got married. Then, in a horrible turn of events he was redeployed for the first 15 months of their marriage. I'm happy to say that he's finally home, and they're now starting their life together. My sister says that if they could survive all that, then they can certainly survive marriage!
I think it takes a certain type of person to do well long distance. You need to be able to have long phone conversations and let the other person know that they are always on your mind even if you're miles apart. Also, it's good if you can have supportive people around you. I lived with my older sister during her final year of med school (aka her first year of marriage), and we had to celebrate her first anniversary together. I know that I was a horrible substitute for her husband, but I also know she was glad that she wasn't alone.
I know that the whole thing was extremely hard for my sister, but she's now happily married and couldn't be more proud of her husband, who is now a captain in the army. Obviously this was a very unique situation, but they're living proof that long distance can work.