This question came up on The Violinist forum – and I think everyone has their take on the subject. I would say that the decision to leave a teacher is a personal one – it may just be time to change teachers. Also, if you have reached a good standard I have always found it useful to take on a student – it really forces you to show good technique for the student – and by doing so, you keep yourself in check. And I agree with the other respondents there that there is always more to learn with the violin, and it is good to have at least irregular ‘tune-up’ sessions with a good teacher to ensure you don’t reinforce bad habits. Yes even Perlmann gets other teachers to help maintain good technique.