Saying you are always a beginner is cheating, using a philosophical point. Of course we all strive for shoshin.
But it's such a common thing to do among instructors and traditional martial artists that in and of itself it becomes a form of bragging. How did you earn the right to be so modest? If modesty is an indication of mastery, aren't you just saying "hey look how advanced I am"? Rather than modesty, it's just dishonesty.
I disagree (at least speaking only for myself). Many of us have seen or at least heard tell of the almost god-like Black Belts who won't won't give mere mortals (mudansha) the time of day. Or some Yondan who doesn't think that a mere Shodan or Nidan has anything they can learn something from. Trying to keep a beginner's mind and/or considering myself as always a beginner is one way that I guard against becoming too full of myself as I continue my training.