I would argue that among really good writers, it's not rare at all. The usual course is for an author to keep learning for years, figure out what works well for them, and perhaps lose a little ground towards the end of their lives due to failing health or lack of care.
Similarly, good technologists build a workshop full of techniques that experience has given them, do their highest quality work in middle to late middle age, and then retreat from active building to teach, critique or advise.