When I'm not forced to half-ass it because of other schedule issues, I tend to spend Tue/Wed/Thur just thinking about what I might feel like working on for the week. Often that means thinking about what instruments and mood fit my current mentality (loops/rhythm, piano/synth, Samplr, distortion?).
By Friday I like to have recorded all my sounds and casually played around with how to arrange them. After that I let the sounds bounce around in my head some more and spend a few hours on Saturday and Sunday arranging everything and adding final touches.
I prefer to spend almost as much time away from the sounds as I spend working with them, as a way to keep it fresh and give my brain a chance to think of what we can do differently. All-in-all, I tend to spend about 10 hours over the week actually working with instruments and the computer. That ranges widely by week of course.