G.A. Henty wrote about a hundred books with the same protagonist. He did not, to be clear, write a series of that length; his longest series is three books long, and indeed he only wrote three series to my memory.
Fantasy and sci-fi are legendary for exposition dumps. See, worldbuilding and its ilk is often quite important to the story, even to the point of being a part of the pitch to get the reader interested, but too often it