Longer Books & Series Going Out of Style?

I recently read an article about how the average length of published books decreased by about fifty pages. It got me thinking about how longer series that tell a larger story through multiple books retain readership?

How long is too long? There are some series I love the length and others I lost interest in. Harry Potter is seven books. The Percy Jackson series extends over ten books. Dune is another long science-fiction drama. I haven’t read the Wheel of Time, but that is a longer series. Brian Jaques builds a world of mice over several books as well. Game of Thrones is five books.

I’ve read almost all of Brian Jaques’s tales of Redwall and surrounding areas. But I could hardly make it through the Pendragon series. I think I got seven books in. Maybe that’s why the Wheel of Time is such a daunting task. It’s fourteen books in length, and the only thing I hear about the ending is that Brandon Sanderson finished it. I’ll admit I’ve brought the first book because I really enjoyed the t.v. show. So stay tuned. (I have to finish my current books first).

The length of a series might depend on the genre, where it is acceptable to see longer storylines.

What is the longest series you’ve read? Are there any that you tried and lost interest in?