But why do you assume that I am "setting myself up to get paid way less"? As I said, I have no evidence to suggest that I would command a significantly higher rate on a daily or weekly basis than I do now. However, not taking on any gigs that aren't really full time (but can be combined at my discretion with others that also aren't) would certainly have cost me money in the past.

I can see the argument for fixed price vs. T&M billing. I guess I just don't see why going as far as daily/weekly billing doesn't net a significant part of the downside (no hard limit on hours vs. compensation, no clear cut-off where clients have no claim on any work I do other than for their project) without necessarily netting much upside.

As I said, perhaps that's the way the game happens to be played in whatever markets you've been working in. I'm certainly not saying you're wrong about your own situation. I'm just suggesting that your comments here are black-and-white but don't necessarily apply to everyone else's situations as well.

You may be 100% correct, but have you ever experimented with his advice? Don't think you're right. Try it. Experiment and know what works best.

I couldn't experiment with his advice with my current business model. Working on a longer time interval (daily, weekly) when you want to deal with multiple clients during a single interval is a recipe for unhappy clients and potentially legal fees.

If I am billing weekly, but in practice I do 2.5 days of work for each of two clients, do I bill both for the entire week? Most of Thomas's arguments for rounding up in these longer increments on the basis of opportunity cost demonstrably don't apply in this context, because clearly I can use the other time to work for another client. The best outcome I see if someone I'm working for finds out is that I have an unhappy client and probably lose the contract -- which is fair enough, frankly, if I'm billing for a week but only actually working for them for half of that time.

For the avoidance of doubt, I'm not arguing against having a reasonable minimum billing period so clients don't mess you around and so you can manage your time sensibly. I'm just challenging the notion that "hourly" is not a reasonable period for some of us, and pointing out that "daily" or "weekly" can have serious drawbacks too.