Maybe instead of measuring tasks/projects in man-hours, how about mind-calories? For example, 100 mind-calories is equivalent to 1 hour of work that is of the mental intensity that 60 hours of it in a week would make you too tired to do anything outside of it except casual social and leisure pursuits. i.e. The average American white collar worker uses 4,000 mind-calories toward a job that he or she is okay with, and has 2,000 mind-calories left for errands, commuting, and dealing with other stresses. If he or she tries to use more mind-calories, then he starts to get worn out, agitated, and possibly neurotic.
Right now, I've for example, scheduled myself to do 30 hours of work on iPad development a week. This seems totally manageable on the surface, but it really depends on what I'm doing during those 30 hours. If it's something like programming, which is a 150mc/hr activity, then those 30 hours are actually a 45-hour work-week. That's one end of the spectrum. At the other end, let's say, I'm doing mock-ups in Photoshop, which is something really fun, its more like 50mc/hr. And then if I'm doing QA with my friends, I actually gain energy back, and so that's like -20mc/hr.
I think I prefer these kind of units as opposed to man-hours, at least when making plans for my weekly schedule. Sometimes I take on a task that seems harmless enough, and only requires 1 hour of work, but the stress and agitation involved may actually take out 500 mind-calories.
This idea also explains to me why you see perfectly smart college graduates becoming "starving artists" waiting tables while working on their real craft after hours. It's because waiting tables is a mindless activity, maybe 50mc/hr for most people. I always wondered, "why don't these bright kids get some nice-paying marketing job during the day, then work on their hobby in the evenings and weekends?" But this is why. There's no juice left to be creative.
