It can work for a while if there's a light at the end of the tunnel, a time when you can expect to be together. Military families, Foreign Service families, sometimes academics, and others do it all the time when one person has to travel or for some reason live someplace else for a while. My husband and I did it for about two years when he had a project in Cleveland and I was in the D.C. area. He would fly down about every other weekend; once in a while I would fly there. For two adults, it was workable; I would not have been happy doing that if we had had children. Plus we did see each other fairly often. It was a LOT easier on us than it is for military and FS families when the spouses can't see each other sometimes for as much as a year.
Re: your situation, DeafCaroline, sounds to me like the guy who met the "church girl" was probably being very honest; he just met someone who was a better fit for him. That happens, long-distance relationship or no. It hurts, but at least he was honest about it and saved you the expense of going to see him.