[pjungwir]

One of my favorite books, Managing the Professional Services Firm by David Maister, talks about how professionals of all kinds tend to need acknowledgement and recognition of their accomplishments, and as soon as they accomplish one thing they move the goal posts further out. I don't recall whether he invokes impostor syndrome explicitly, but that's what it sounds like. No matter how accomplished/experienced you are, you always have a further goal and are seeking proof of your expertise.