dont know but if you think abou the fact das the guin saga the longest novel of all time is
[over 1000 books] its not completed and i never will, because the mangaka died in 2009
she was a wonderful woman and guin saga is the father of berserk and other stand alone spin-offs.

there is so much to ell about guin, the pharos twins, red star, lady amnelis
it would be enough to pull off a over 500 episodes like one piece.

according to wikipedia "as of the author's death in May 2009 the total stands at 126 volumes, with 21 side-story novels."
not quite a thousand lol, but still very very long, considering the longest series i have read is the Shannara books which are like 20 books or so i think.