GMAT Strategy

I currently have studied around 4 weeks for the exam and am getting ~680 on my practice CATs. For the schools I am applying to, I need to be around the 700-720 range. I want to apply by round 2 for all of them, which would be in early Jan 2011. I am signed up to take the GMAT on Dec 16th, which would only give me 1 shot on the exam unless I want to apply round 3, which I have heard is a death sentence. Should I schedule an exam in the next few days and see how I do and if I don't do as well as I had hoped, I can then retake it in early Jan 2011 and still make round 2 deadlines or should I just study for 2 more weeks and try to do the best I can with 1 try? Thanks for your replies!

Give the test whenever you feel you are ready to hit ur target. Noone but you can gauge ur readiness.