Extract from a post by Jack Eason:
Here is a question for all my fellow writers, both published like myself, and those who just love to write for the sheer joy of doing so. How many hours do you spend writing each day and how many words does it involve?
Ever since I changed the way I write from how I used to in decades long since past, when I would spend all day and long into the night to achieve a daily word count in the thousands, I now stick rigidly to a short but extremely intense daily session when I have a new story in mind.
I find this is the method that works best for me. If you are wondering how long; these days I limit myself to adding no more than one to two hundred words per day.