I responded to the professional development aspect of Patio11's comment. My point being that seasoned professionals do have wisdom to impart on less experienced colleagues. I used myself as an example but the point made is clear (I think).
Even if I really am not a better teacher now than I was 17 years ago the point is still true. Well, in order for the point not to be true one has to believe that there is no wisdom gained from experience is teaching an that this is universally true. I know of no profession in which practitioners do not generally get better over time. Indeed,there is no profession in which no practitioner gets better over time.
So what is the point of requesting that I prove that I really have gotten better over time? It's not germane to my point unless one believes that no one ever gets better over time in teaching.
Look, my Mother has 2 PHD's in education and often does professional workshops for teachers. However, like most forms of professional development her workshops are both expensive and their value is hard to quantify. So it may pay better than her normal job but as she says it's of limited value.
Programming is a lot like teaching it takes a few years to get up to speed, but vary quickly years of experience stops being a useful metric.