I could not do long distance for 5 years. I did it for one, and after realizing how much another 4 years would suck, I decided it wasn't worth it. Also, there wasn't a clear end-date in sight - which makes things even more difficult.
I also think it depends on your partner. I had a needy one. I was made to feel guilty when I concentrated on school. We skyped daily and it started feeling like a chore.
He also said he'd never move to the States. While I have no idea where I'll end up working in the future, I am not eliminating job possibilities just because of his stupid Canadian superiority complex.
I am much happier dating someone local now.