Are you an MS-2? You're pretty ambitious, huh? If you were an M-3, you would not likely be asking this question so late in M-3 year, as you'd already be done with most shelf exams. I think USMLEworld could be useful in prepping for shelf exams. However, if you did each section by the end of M-3 year, you'd already have used up the questions by the time you're an M-4 and start studying for Step 2. Plus, you'd have to keep renewing your USMLEworld membership. Three months cost $175, so it would cost a lot of money to renew it for all of M-3 year. I think you'll be OK if you just stick with one of the review books (i.e. First Aid, Blueprints, Case Files) and use Pre-Test for questions. I would hold off on UW until you're studing for Step 2. That way you can mix up all the questions and you won't be going through questions you have already reviewed.
