At the moment I'm a freelance software developer, and I take on multiple projects at once. Right now, I'm working on three projects, and typically end up spendi

At the moment I'm a freelance software developer, and I take on multiple projects at once. Right now, I'm working on three projects, and typically end up spending 4-6 hours a day on billable work. I can put in more, but after a point, I can feel my productivity drop off. Realistically, I end up completing 20-25 hours of billable work a week (and probably another 10-15 doing stuff that isn't directly billable). I could spend more time working on billable stuff, but I find that there are heavily diminishing returns after that point. Sure I can get in more productivity for a brief period (a few weeks max), but there is always debt to repay. A lot of people tell me that they are looking for someone who is "half time", which to them means 20 hours a week. I've tried to explain to them that I don't schedule 40 hours of work in a week, and that for me "half-time" is 10-15 (productive) hours. A lot of people won't accept that. I'm finding that it's easier to tell them that I'll work half-time, get more work done in 10-15 hours than most people would in 20, and then bill them for the time that I actually worked. If I'm getting the project done, then they aren't going to complain that I'm billing them for too few hours. That obviously doesn't work if they are expecting me to be on-site 20 hours a week, but in my case (where I work in my own office), it seems to be ok.