Well! That depends from person to person. My friend prepared well in 2 months while I had to toil day and night continuously for 5 months to achieve my target GMAT score.
But guys, the important thing is 'not to quit' and keep up the good work- working hard and smart on the exam. One thing is guaranteed for sure- 'your efforts will never be in vain. I started my GMAT journey with just a score of 610 on my first attempt. It was not going to anyhow land me into my target b-school, I knew. So I had to formulate strategies and I really did put a lot of effort into maintaining and revisiting my
error log. This time, for my second GMAT attempt,
I really worked hard on working smart and that made all the difference for me.
So, never give up, evaluate your strengths and weaknesses thoroughly. And act upon your strategies by being realist.
Practice, Strategize, Excel...
Hope it helps!