I have one main client that will basically pay me hourly as much as I'm willing to work for them, but then I also try to take at least 2-3 other clients on each month just for diversity. The smaller clients I typically charge by project rather than by hour, and so far I've been able to get my rate on those after the project is done in the lows 100s/hour range. For me personally I don't know that I could get my schedule completely full of work like that, but it might be possible I suppose.