Since I live in a university town, where my husband once taught, many of my friends and acquaintances are or have been professors. Many of them are now retired. They are intelligent, interesting people, highly knowledgeable not only in their special area, but having a breadth of interests.
However, for some after retirement, there is a condition I call Professor's Disease.This disease comes from having classrooms full of students in thrall to the professor's wisdom for some thirty years or so. The main symptom is "I'll talk, you'll listen," resulting in one-way conversations. They are not necessarily boring, but when one is on the receiving end, there is a sense that there may be a pop quiz after half an hour or so of listening, or pretending to listen, to what amounts to a sort of lecture. These folks can go on and on for some time, perhaps for fifty minutes, the usual period for a class. In the case of a seminar, it could be two hours. I've often felt that if I raised my hand, I might make a comment or ask a question, but I'm afraid that might encourage an additional flow of verbiage.
In good weather they can be seen downtown, like a pointer at a pheasant hunt, holding one or two people immobilized, except for the faint nods, at bay while offering the latest scholarly take on politics, the state of higher education, etc. etc. etc. it must be terrible not to have those classrooms in one's life any longer.
I mentioned this disease to a friend, and she said that on occasions when she is at social events and doesn't feel like engaging in conversation, these are the people she seeks out, knowing that the ball is in another's court, and she can relax and enjoy her drink and appear to be sociable. And, as I mentioned, they can be interesting.
They are not good at listening, so if their hair is on fire, they may not hear what you are saying. That's why it's important to keep a drink in hand, preferably non-alcoholic.