Hi shash1990,
Since you've taken just 2 CATs - and scored 600 just once - there's no way to say for sure whether that recent result is an accurate reflection of your current 'ability level' or not. Statistically-speaking, you would likely need at least another 1-2 months of consistent, guided study before you could get to the point that you could consistently score 660+. If that truly is the minimum Score that you would apply with, then you need to think in terms of the application deadlines that would give you the proper study time and the best chance at earning that type of Score.
If Rotman is your first choice - and that last deadline isn't until early March - then you might want to consider building your study timeline around THAT application goal.
From your initial post, I assume that you plan on studying full time going forward. However, you have to be careful about confusing "quantity" of study with "quality" of study. I've never asked anyone to study 40 hours a week - and while it's great that you might have the available time to study that much, you would run the risk of 'burning out' before Test Day (and that is something that we want to avoid). If you are going to try to study that much, then I suggest that you take one hour "off" for every two hours of study. For example, you could study for 2 hours, then stop for an hour, then study for another 2 hours, then take an hour off, etc.
I suggest that you take a day to decide how you want to proceed with your studies. One month of consistent, guided study might be enough to get you to a 660+, but if you could give yourself more time than that, then your chances at earning that type of Score would greatly improve.
GMAT assassins aren't born, they're made,
Rich