The 150 Hours Rule of Thumb
"One of the most fundamental concepts to understand about your GMAT prep is how much time you'll need to devote to your studies. Prior to the recent test change, which saw the inclusion of the Integrated Reasoning section into the GMAT, we recommended 100-120 hours of prep time in order to achieve a 700+ score. With the new section added, however, and the extra skills study that goes along with it, we recommend devoting 120-150 hours of prep time to land that same sort of score."