I am so sorry for your loss. Your dad chose how he wanted to live, and as a result he was healthy and strong until the end. I'm in his age group, and I've had friends who have spent years doing what the doctors told them, taking pills and receiving treatments that were often as debilitating as the disease. Some undoubtedly lived longer lives than they otherwise would have. Quality of life? Sometimes the trade off isn't worth it. Others ignored medical attention. There are no easy answers. Just be happy your dad chose his own path.