Novel Series That Last For Too Long

I've ranted about this at length elsewhere and at much greater length than I tend to post here.

I read a lot of books. A good trilogy really gets me excited.

That said, however, I'm done with Honor Harrington. I'm done with Harry Dresden.

You reach the point where you no longer fear for the protagonist. I thought the first few books in both series were excellent. But, by the time you start hitting book eight, you realize that there's no reason to fear for the character's survival anymore.

And yes, I know that (SPOILER WARNING) Harry Dresden was killed off at the end of one of his books. But you can't write The Dresden Files without Harry Dresden, so he'll be back. You'll see.

Honor Harrington exists in the "Honorverse." And you can have Honor's universe without Honor herself - and David Drake seems aware of this. He has expanded the universe a bit and has written books that feature other characters. Whether this is because he's bored of the character (like I am) or because he wants to make sure he can kill her off and still have a career ... well, it makes a difference.

The Hitchhiker's Guide to the Galaxy was great. But each successive book lowered its quality compared to the preceding book to the point where it was a real struggle to get through Mostly Harmless.

Writers? Give me a trilogy. In a trilogy, I can still fear for the protagonist. Don't go much past that, though. Please.