Can extramarital affairs last a lifetime?

Can extramarital affairs last a lifetime? I had an Aunt and Uncle that I adored. My aunt was stricken early in life with heart disease and emphysema. My uncle was her care giver for years. They truly loved one another and he was always very attentive. My uncle got throat cancer at 80 years old. He told me then that he had a girlfriend that he had been with for over 50 years and asked me to visit her with him. I did and understood their love for one another. He wanted me to meet her and stay in touch with her as he was in treatment and I did. He ended up passing away and left things with me to give to her. I know she was devastated. He wife, my aunt passed 4 months later. I am still in touch with his friend. As an older person I understood his need for a partner outside of the marriage. I would have had a problem with it when I was younger because I believe if faithfulness. As I have aged I realize connection is what life is all about. He was loved and loved two women.