My first T is not over 75 and practicing. May not be nice to say but I think retirement would probably do good at least to his clients - he is really not very intact cognitively anymore. I know that his supervisor was ~90 when he died (of Alzheimer's) and was still practicing two years before his death. Also, one of his colleagues, his age, died recently and was still working a few months prior. I understand if they are passionate about their work and find it hard to stop but I see it as a form of responsibility to voluntarily end it when they can no longer do the job properly. Maybe they believe they can still sit there and listen, can't make a clean break with clients, or I don't know. I guess, for some, clients are also the main source of human contact and it gives them a sense of being needed.