I would say at least one pt per week but no more than 3 or 4 pt per week because you need to make sure you have good quality of time to blind review every question that gives you trouble during the PT and avoid burn-out.
I know 4 attorneys who have crafted interesting, meaningful careers outside of big law that give them lots of money and a good quality of life. So, in short, I agree with Nicole.
... the wrong answer is wrong. Quality is always better than quantity ... , quantity without any compromise in quality is ideal). Doing 10 questions ...