General rule around here you don't want to go over two, maybe three pages tops. People want to read your story, wank and move on. Don't let that stop you from writing a long story if just be prepared for a low score and plenty of haters.
Note: Once you transcend ten pages your score will go up about .30 for every three pages after that. Anybody who was enjoying your story enough to grind that far will most likely give you a five because they absolutely loved it and the haters usually don't care enough to click to the end JUST to fuck you over. But that's just friendly advice.
"Ask not the sparrow how the eagle soars"
"Be bold with your intentions, and delicious with your sins."