So, an author named Ameaner wrote a huge, multipart series that had three multichapter sections.
The first was called Dad's the Man and it was 15 chapters. The second was My Other Mom and that was 15 chapters. The third had characters from both stories and was called Sera. That was about 35 chapters.
I can't give away too much here, but things are a little darker than they seem and by the end of the comprehensive story you'll realize that it could have as easily fit into a different category than incest.
It was extremely well written but it turned out to not to be my cup of tea. That doesn't mean I can disregard the authors talent though.
Going just on length tends to favor a "wordy" style, which may or may not be what you're looking for. That being said, here are some longer ones I liked.
(Note: about 3,600 words per page in a literotica story)
dad/daughter:
36,161 words: MyCuriousNature's A Father's Love -- excellent