I've been asked, due to how much I'm able to produce, if I sleep. Yeah, I do. I need 7 hours, or I'm pretty useless. And my productivity has plummeted since I became a father (that's not a complaint). Back when I banged out The Master Of Verona, I had a lot of 10,000 word days. My best was a 22,000 word day.
These days 5,000 is a good day. (Today was good). But I'm also a better writer, and better editor, than I was ten years ago. I'd rather have 5,000 good words than 20,000 ones that have to be pared, replaced, and eventually cut. (The second draft of MoV was 300,000 words. The one St. Martin's bought was 192,000.)
I don't know if that makes me prolific. But it does keep me busy.