To get an idea of the required prep time, take an official practice test: https://www.mba.com/the-gmat/download-fr ... tware.aspx
It may be the case that you're already scoring above your target score, in which case you may not need to prepare at all
Or it may be the case that you're hundreds of points away from your target score, in which case it may take several months to reach your target score.
If anyone is interested, I wrote an article on the importance of taking a practice test early in one's studies: https://www.beatthegmat.com/mba/2013/05/ ... st-already
Cheers,
Brent














