How long would you stay in a marriage with a cheater?

My parents stayed married for 17 years. My mother is the one who had an affair. In my opinion they should of divorced long before she cheated. They stayed together for us children. What really is bitching is us children wanted them to divorce 7 years prior. We wouldn't have cared at all. It would have been better than watching her cheat and my dad driving us in the middle of the night to a night club 50 miles away. At the night club we had seen her car and her dancing with a handsome looking man. She said she was at Bingo! I forgive my parents as that was long in the past. But, my dad never remarried because he couldn't forgive her until is death. What a bitch to deal with until death. He always loved her!