I think the above advice is good. With a 710 already, you aren't going to gain anything by doing another "practice run" on the test. And while schools might not care that you cancelled an exam, I don't think it's worth the risk.
Also, I'll second the question that was raised above: why are you retaking the test, anyway? 710 is good enough for any top program. Anything that high will get your application serious consideration; in other words, if you get rejected, it won't be because your GMAT score was too low. At some point (say, over 700), the rest of your application becomes a lot more important than your GMAT score.
My experience with students retaking the exam has been that the vast majority don't do much better, and some even get worse. If you put in serious study the first time around, and you're already at 700+, I don't see any reason to take the test again. Just my two cents...
Hope this helps!
Jim S. - Veritas Prep GMAT Instructor (Los Angeles, CA)