I wrote the first draft of my dissertation Emergent Design at http://emergentdesign.net in six weeks. Then it took ten or eleven months to rework it so that the english was acceptable with my wife as my editor. We argued over every sentence. After I was done I did a diff between the original draft and the final passed dissertation, there were a few words that went untouched, like I noticed that the phrase “In other words, . . . ” on one page remained untouched throughout the editing process. Not sure how those words were spared.
Quora answer: How long does it take to write the first draft of a book?