I just checked my Audible library and my longest book is Ayn Rand's "Atlas Shrugged", a little over 63 hours long. I have a lot of books over 40 hours long, too many to count at a glance so I didn't bother.
MY reading and listening pattern has always been to read a long book, the longer the better, and then read a few short books and then another long one. I vary that a lot and it's not something I do intentionally. It's just how it seems to work out.
I have Michener's "The Source" on my Kindle at the moment and I'll probably reread it in the near future. It's 1100 pages. I read it when it was first in paperback and a decade or so I listened to the audiobook and soon I'll read the Kindle version.
I don't judge a book by it's length but there's something really nice about a really good really long book.
Barry