When Daniel Kaplan reached the mandatory retirement age of 70 at Proskauer Rose, he never contemplated calling it a career. Instead of following most of his peers, he moved his busy corporate practice to Akin Gump Strauss Hauer & Feld, which didn’t have such a policy.

Now 87, and two more Am Law 100 firms later, Kaplan maintains a transactional practice at Dorf & Nelson, a 16-lawyer firm near his home in Westchester, New York. As senior counsel at the firm, Kaplan billed roughly 1,600 hours last year, and is known as a business generator and mentor.