My oldest PPL student was 72. I considered him one of my best students. There was no question that he took longer to learn the hands and feet part of the training but that was more than made up by his maturity, lack of ego and his enthusiasm.
He wanted to learn to fly for his whole life and had finally arrived at the time in his life when he had the time and financial resources to start training.
After he got his license he continued to fly regularly for 5 years. At that point he decided to hang up his spurs due to deteriorating vision. He could just barely pass the vision part of the medical but he no longer felt he was safe to fly.