I've written a book 1 in month. 300 pages. No editing. I've written a book in 6 months, 200 pages, edited. Some idea just come. Others take work. I don't know how it c an take 10 years to write a book but then again nothing of mine is regarded as being very popular. I like that King writes a book in about 3 months. If that's all your doing I think that's a good goal. I've met a lot of writers who do a book a month because they are highly competitive on kindle.