"I find that at about 30k words, it's good to step away for awhile. At this point I usually skip to the end and flesh that out. Then when you come back to your story, you have a better idea of where you're going and how to get there."
"@TD I recently had a similar experience. I was a little further along in my story but really plodding. Writing the end suddenly helped me fill in what I miss missing. I am now a mere five outlined chapters from the end :)"