That's the question that I keep asking myself lately.
When I started the my first novel, during last year's NaNoWriMo, the extent of my recent creative writing had been a few writing exercises, none of which I would show to anyone but the hubby. So imagine just jumping in to write a novel with nothing but a basic outline, excitement and determination. Excitement and determination got me through the month of November (meeting the goal of 50k words in one month) and working to finish the story (total length of 125k words) in February. As for the outline, well that had fallen by the wayside in the first week.
Since then I've read some more on the craft of writing ... author blogs, Flogging the Quill, and portions of Story. With this new info in my head, I went back to the ol' computer to begin the revision process, envisioning a few months worth of work.
After getting started, all I have to say is "Yikes!" While excitement and determination got me to the end of the first draft, it didn't do much for a well crafted story. I've encountered truly cringe-worthy passages, painful I tell you. And too many craft issues to list. So now I'm working on improving the story so it makes sense, is realistic, has tension & engages the reader.
It's taking much longer than I expected. My original estimate of a few months has followed the same path of the original outline: out the window.
How much longer until I'm finished? I have no idea. Well, let's look at it -- there is family to tend to, the holidays coming up, another NaNoWriMo this November and countless other things that are bound to crop up. But I am committed to finishing it.
So the answer I give myself: as long as it takes.