There's an interesting post about about writing productivity over at Grumpy Old Bookman. Michael Allen talks about how he's managed to get things written over the years while writing part time. He reckons:

On average, and it was very much on average, I found that writing a book took me three hours per thousand words. Roughly one hour to plan each thousand words, one hour to write, and one hour to revise and polish. Marketing and publicising were extra.

Within that average, I once completed a 75,000 word novel in 125 hours, and another novel, about 100,000 words in length, took me 600 hours -- largely because my then agent wanted revisions.

He goes on to say that it is quite possible to complete large projects, a little at a time, and mentions that that the hours he spends writing have not increased as dramatically as might have been expected since he retired.

...even if you do win the pools, or suddenly get given a contract which is sufficiently valuable to allow you to give up the day job, you may find that the number of hours which is available for writing in a given week does not, somehow, increase in quite the dramatic way that you might have thought.

What you may find is that that slaving over a word-processor, without any kind of human contact, for eight or more hours a day, is a profoundly unsatisfactory way to live your life..

The entry it well worth reading for anyone who is frustrated at having to juggle writing and making an income, which is just about everybody if the truth be told.

I don't think I can attain the production rate he cites, however. Not even working as a co-author. (Although the way we work, with each of us essentially writing and/or rewriting everything does not save as much time as one might think. Arguably it takes more time. No doubt, two people doing research saves both of them time).

Although I keep careful track of my actual hours for legal writing projects, when it comes to fiction writing I keep only a rough record of days worked. In the case of Five For Silver and Six For Gold I worked at research, planning, writing, rewriting, and dealing with editorial suggestions on about 80 and 100 days, respectively, spread out over around five months.

Some of these days were very long, some were fairly short. It would be difficult for me to estimate the hours involved, but I am certain I do not write 1,000 words in three hours.

The reason I am most interested in the number of days needed is because I like to write scenes at one go. I don't always manage, but usually I will plug along until I've finished, at which point, how many hours it might've taken me is irrelevant since I practically never have energy or inspiration to tackle a second scene the same day.

Joe Konrath I fear would laugh to read this since he finished his last book in 35 Days!