I think it is possible to have a serious relationship long distance, if it is moving towards one that is together. I had met a girl here on this site some years ago. We chatted at first, started to become close. Became closer, made plans to meet. I met her in Ukraine. Then she and her sister came to visit me. This all happened over several months. We started the application for a k-visa and she came to stay for 2 months. Things eventually broke down, but it was a nice, serious, loving relationship in person and over the distance, while it lasted.