Well I believe you can surely and as much as you want. Just to demonstrate, for the first time I gave GMAT prep I scored 480, yes and then I went on to score 710 without enrolling for any prep courses. All I had were some good books passed on to me by my senior and rest discussion forums. So If I can make it, so would you. All you need is whatever time you are going to give, be sure to devote your heart and soul to GMAT and your score will definitely improve.

Just for the start, I would advice you to again check back your mistakes in the 1st test you did. Once you know which sections you had your mistakes,its quiet easy to work on them

Hope this Helps

GMAT 740: More specifically, how did you get from 480 to 710? That is a huge jump. I am have a hard time breaking 550-560. The highest has been 630 on a practice test. What were you weak on when you got a 480? Q or V? Also, how long did you retake the exam? And how did you approach the test differently the second go around? Any advice would be helpful for people who in the same boat as JPWV and I.

Thanks