Can extramarital affairs last a lifetime?

Can extramarital affairs last a lifetime? I had an aunt that had an affair with a married man for most of her adult life. I found out long after I had married and had children of my own. Supposedly the gentleman in question had a wife that had either an accident or injury that left her completely dependent on him. He refused to leave her to the care of the state, and no family was available to care for her. He had met my aunt at his work and over years had fallen in love with her. She never married anyone else, and never had children. I always felt a bit sad for her as she was a lovely woman and deserved a full marriage. She made the best of it. I know she was devastated when he passed.