njrick:
Anywhere from a couple hours to ten years.
As I have only been writing for three years, I am not quite sure about the upper end of this interval yet, but it sounds about right. There's a lot of factors involved in how long it takes; I find, e.g., that I usually write faster when the action gets going — it's the build-up, getting the characters, the setting and the atmosphere right, that takes the longest. Unfortunately, I believe in long build-ups....