When I first got out of law school - about 30 years or so ago, we had several attorneys who were over 80 who kept offices, came in every day, wearing suit and ties. At my universities, there have always been emeritus offices, and even when I was in undergraduate and in law school, we had a lot of academics in their 70s and 80s who came in and worked on writing papers, teaching etc.
I don't think it is a baby boomer thing necessarily.