I've taken quite a few Blablacar (car-sharing website) trips since moving here in 2013. My Spanish is at a level where I can converse with the other passengers fairly easily. One of the most common reasons Spanish people use Blablacar on weekends is to see their partner. Many, many people here are forced to seek work outside of their hometown, thus putting distance between couples. Some take Blablacar for hours, one direction, just to be able to spend a couple of days together. I recall meeting one man from a tiny town near Jaén, visiting his pregnant wife every week, while she worked in Madrid. His story is one of many.
My spanish friend Vic is an English teacher, who receives a new placement every year. Her life is similar to anyone's in the NALCA program, except she stays in her chosen region (Andalucía) and changes cities, whereas for us auxiliaries region placement can be a craps game. Her difficulty in maintaining a long-term romantic relationship stresses her out. She'd like to stay in her hometown and establish something, but it would require taking difficult career tests that she has no appetite for. So she continues with the instability of her career and personal life.
Do long-distance relationships work? Looking at how many Spaniards do it, you would think it's possible. Based on personal experience, and survey results, I vote probably not. Although I only tried it once, and it was with a dude I met at a rave, and it was only 3 weeks after we met that it was over so..... that's been my one and only experience.
I asked a friend, who travels a lot both for work and pleasure, if it's possible for someone with his lifestyle to have a long-term relationship. He believes so, if the person is understanding and has a similar lifestyle as him. It's a difficult thing for a single person to keep aligned: a love for travel and a desire for a stable relationship.