1) they tend to be impatient with ‘mere mortals’
2) they tend to reinforce what they already believe or trust they know
3) they get overly defensive when others challenge them
4) their listening skills have tended to atrophy
5) new ideas are often seen as a threat or source of discomfort for them
6) frequently they tend to hang around with people of similar stature
7) they have become over-reliant on the approach that enabled them to become an expert in the first place
If these signs are prevalent, it portends an expert in decline.