well , this is a diffuclt question to answer.
basically we have to take in account 2 things: on one side, many students report that even if they take a good cat (MGAMT KAPLAN) then during the exam there is a consistent difference with the real score. I guess because the concept are the same but the practice material, even the best is DIFFERENT, why ? I do not know. Considering also other elements: time pressure, nervosism and a bunch of variables.
On the other hand if you take too much exam MBA programs interpret this as a poor ability to process information quickly. Sincerely speaking I think that 4 times is a border line to take the GMAT. Moreover, is important to have a good balance between verbal and quant score, albeit is more important the verbal part.
maybe someone knows more than me about, but more or less this is the picture.
Good luck