ZERO. Waste of time for me. And I don't read the casebooks (I do skim them) or even go to class regularly (I probably miss 1/3 of my classes). I just cram for the week before exams, creating streamlined outlines, and it seems to work for me.
After 1L, when I crashed and burned on the classes that I spent the most time preparing for, and aced the class that I rarely showed up for, I figured out that it is more effective in my case to just focus on the big picture topics at the end of the semester rather than get bogged down by irrelevant BS throughout the semester.