I only blitzkrieg through an PSAT/SAT whenever I want to get a measure of my true score.
Usually though, I just do a certain section a day. If it's Monday I'll just attack all the writing sections and make sure I thoroughly understand what I got wrong. And what I got right by guessing
I make sure to mark up my answers too - a check for questions I think I got right, a question mark for questions I guessed on, and an "X" for questions I just don't know.
Taking a full-length SAT is a major time drain. By the end, you'll be too tired to really go through your mistakes one by one and carefully. Break up some of your SATs and work on them section by section.
Be sure to leave some left over though! You'll probably want to know your "true" score before you take a real SAT