I just pulled up the last year's worth of consulting invoices and yes, it looks like I managed to bill an entire 40 hours once in the last 52 weeks.

I have a personal policy of only billing for the time I'm creating value. So if I boot up, fire up the IDE, sip my coffee, pull up a bug report, then proceed to browse f'ng Hacker News for 2 hours, I don't charge my time. Similarly, if I notice by lunchtime that I'm just plain not smart enough to program computers for money today, I'll stop the clock and go climbing or something.

So yeah, I bill 20-30 hours each week, but they're good hours. Back in my salaried days I'd often find my butt in the Aeron for a good 60 hours a week, much of which was spent debating where to go for lunch, reading the internet, and maintaining the corporate HalfLife server. I doubt I got any more productive hours in then than I do now.