I don't keep track of exactly how many hours I usually write. I know I've probably written at least 2 or 3 hours (possibly more) a day this summer while I'm off school. My goal is to write, on average, a minimum of 1,000 words per day, though I usually write more, depending on how intense the scene is. I usually do a light revision on what I wrote the previous day, write until I finish the chapter or scene, and perhaps start the next one. There's some days where I only write a few hundred or under a thousand words, while there's been days that I write 2-3,000. I figure that if I aim for 1,000, I can realistically reach it and write even more.
Now, once school starts on September 5th, my routine will probably change. I'll probably write a lot less on weekdays and write a lot on weekends and holidays. That's life, so I'll have to work it in. Frankly, I've written so much this summer that it makes up for the days during the school year when I don't write as much. It averages out to 1,000+, though.
