There's an editorial by Stanley Pranin over on Aikido Journal
that I think is relevant here.
I voted yes. Mr Pranin is critical of a certain kind of instructor of long experience in this article, and I agree with his point of view. I dont expect a teacher to be Arnold Swarzenegger, and I dont expect them always to be in the best of health, but I do expect them to set an example. You can't blame a person for their own ill health, especially in their later years, often its just a matter of luck. But a person whose lack of practice or obesity exacerbates their state of health is hardly setting a great example to those who look up to them.
Recently I was lucky enough to attend a seminar in my home town taught by Mr Senta Yamada. Yamada sensei is quite an elderly gentleman these days, but his practice is still both joyful and vigorous. So much so that when he talks of the benefits to body and mind of long practice (this is a man who's been practicing judo for 70
years, and aikido for almost as long) there is no doubt that he himself is an excellent example of what he's talking about. Inspiring.