i don't know anyone specifically who has taken it 5 times, although in my opinion, 5 would be reaching the "limit" that adcoms are comfortable with - especially since there was such a minor improvement on your last 4 tests. if you do plan on retaking it, my advice would be not to do it right away, and instead study using the resources on this website. plan to take it in the spring or summer after a few months of studying - you should be able to crack the 700 barrier then.
also one myth to note - if you have an ordinary profile, a 700 won't be any different from a 660 or an 800 for the top schools (top 10 schools). if that's the case, then you should really focus on custom tailoring your essays to show a unique / different side of you, rather than just focusing on improving your GMAT score
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