I have a good friend (and a fine colleague) who says he's a "binge writer". (http://www.jlake.com/) He will write for hours and hours and for days and days. Then, he tells me, he stops. He doesn't write at all. Jay is a hare.
I'm a tortoise. I write every day (yes, every day. Sunday, birthdays, holidays). I don't write for hours. Two or three contiguous hours is a lot for me normally. I have reasons for this, of course: I excercise rather a lot, I have a dog who needs lots of attention, I have a house to clean, lessons to teach, meals to shop for and prepare. All you moms out there will understand, and not a few of you dads.
Out of curiosity, I compared Jay's output to mine. I can't give you some exciting number, because I'm primarily a novelist, and he writes lots--and I do mean lots!--of short stories. We've been publishing about the same amount of years. Jay's website boasts of 240 short stories and four novels. Mine--both of them--claim eleven novels, a short story collection, and about fifteen published stories. I think I can safely say that, though it's hard to compare Jay's and my bibliographies, our rate of production is similar.
I tried, a few years ago, to increase my daily output. I kept a little diary so I could see if my efforts were fruitful. A friend (the fabulous writer Kay Kenyon, author of The Rose and the Entire series, www.kaykenyon.com) told me she writes five pages a day, so I aimed for that. Day 1: 5. Day 2: 6. Day 3: 7! Day 4: threw away most of what I'd written. Day 5: resigned myself to my usual three pages per day, or whatever I can get done in whatever time I have.
Partly this is a process issue. Even when I'm not at my computer I am, like most writers, still writing. I'm thinking, puzzling out problems, searching for stakes. In my process, I often have to step away from the computer and do something with my hands to stimulate my problem-solving neurons. I can't imagine typing away for hours and hours like the indefatigable Jay. And he probably can't imagine juggling the multiple tasks I set myself, while still getting the writing done. Kay works really, really hard. I work really, really steadily. Jay works in bursts. But we all get there.
So. Do you want a carrot, or would you prefer a few low-flying insects?