Though I cannot speak from experience, I recall reading similar reflections by G.C. Rota in his marvelous Indiscrete Thoughts (p. 203): My late friend Stan Ula

Though I cannot speak from experience, I recall reading similar reflections by G.C. Rota in his marvelous Indiscrete Thoughts (p. 203): My late friend Stan Ulam used to remark that his life was sharply divided into two halves. In the first half, he was always the youngest person in the group; in the second half, he was always the oldest. There was no transitional period. I realize how right he was. The etiquette of old age does not seem to have been written up, and we have to learn it the hard way. It depends on a basic realization, which takes time to adjust to. You must realize that, after reaching a certain age, you are no longer viewed as a person. You become an institution, and you are treated in the way institutions are treated. You are expected to behave like a piece of period furniture, an architectural landmark, or an incunabulum. It matters little whether you keep publishing or not. If your papers are no good, they will say, "What did you expect? He is a fixture!" and if an occasional paper of yours is found to be interesting, they will say, "What did you expect? He has been working at this all his life!" The only sensible response is to enjoy playing your newly-found role as an institution.