I used to have a number of authors that I would read everything they wrote. Unfortunately, they kept writing long after they should have stopped. If you have a series of books, a trilogy is a good number. By book 5 (book 3 if the books are as long as many recent ones have been) of the series, you tend to run out of ideas, plots, tropes, character types, etc. Changing plot 4 from character A to character G doesn’t change the fact the plot is being re-used. I have a friend who disagrees with me as he’s planning a 20-book or longer series. I also realize that many readers would disagree. It doesn’t change the fact that there are only so many ideas, plots, tropes, etc. a writer can use in a series.
This was started last year, but kept getting put off. I came across a writer who wants to write an 11-book series. As far as I can tell, she hasn’t finished the first book. She hasn’t said if she’s going traditionally published or self-published.
Two of my former favorite authors were Feist and McCaffrey. Both kept pushing out books long past the time they should have stopped. I gave up reading them as they long ago ran out of new stuff, other than names.