<p>Generally, just taking a couple of practice tests does not significantly improve your score. Did you actually study some strategies to help answer the questions?</p>
<p>It's not about number . . . it's about what you do between each test. So if you're doing something better that will improve your score, taking it again is always better.</p>
<p>There is no limit, but people tend to not go over 3- there is usually no significant change after that (if one has been studying in between, of course)</p>