It's an interesting thought, actually. When is too much of a good thing simply too much?
John Waters once said something to the effect that no truly great movie really needs to be more than ninety minutes long. I wonder if the same holds true for novels? Certainly there are many out there that are bloated beyond recognition, sort of like Elvis toward the end of his days.
I recommended the current short story collection from him I'm reading. There's one story, "The Man in the Black Suit," that is truly the best I've read from him in years. I told her it was very "Nathaniel Hawthorn-ish." She said she hated Nate, but would give it a try.