Most people take from four to six weeks to review for USMLE Step I. You should be doing active review when reviewing as opposed to just drilling (pretty useless since you have to apply concepts on USMLE Step I).
That being said, there are a few things that have to be memorized just long enough to write them down on the dry erase board. The Pharm formulas come to mind and a couple of epi equations. Other than those, the rest of the stuff is understanding and knowing concepts well as opposed to rote drilling and memorization.
The "Do questions and then review answers" is a good study method as long as you are getting the purpose behind the questions and not trying to memorize specific answers. As Blade said, this is usually more time consuming and you are likely to cover 50-100 questions in 3-5 hours as opposed to doing huge amounts of questions and answers.
Lot's of reviewing for UMSLE Step I is your individual style and how you like to cover material. The rote memorizers will tend to panic when they attempt to memorize mountains of material. Sometimes the reviewers will not cover enough. You have to strike a balance that works for you, make a realistic schedule and stick to it.
