Why so many tests? Also, stop taking so many CATs so close together! (I'm assuming they're close together because if they were spread out over a long length of time, then you'd be forgetting most of the questions, so it wouldn't matter.) :)
Practice CATs are really good for (a) figuring out where you're scoring right now, (b) practicing stamina, and (c) analyzing your strengths and weaknesses. The actual act of just taking the exam is NOT so useful for improving. It's what you do with the test results / between
tests that helps you to improve.
Next, I think the next-best CATs (after ours and GMATPrep) are either 800Score or Kaplan. (And everybody has some errors in their stuff - that's just life. As long as there aren't very many, we just have to live with it.)
There's no way to tell how many repeats you might get. If you're doing substantial work between tests (which is what you should be doing - see above), then you won't see as many repeats. If you're just taking test after test without much of a score change, then you're a lot more likely to see repeats (and you're also wasting your time, because you already know your current scoring level and your strengths and weaknesses - so go do something about them before you take another test!).
Generally, I don't advocate taking a test more than once a week EVER, and most of the time you should have a *minimum* of 2-3 weeks between tests. Every time you take a test, you can come up with at least 2-3 weeks' worth of study material. Read this:http://www.manhattangmat.com/blog/index ... ice-tests/
Taking a test again before you deal with the issues you've identified in the last test is - I'm going to say it again - a waste of your very valuable time.
The *only* time I recommend moving to once a week is during the last couple of weeks before you take the real test, so that you can develop your game plan:http://www.manhattangmat.com/blog/index ... game-plan/http://www.manhattangmat.com/blog/index ... to-review/
So what I'm going to suggest right now is this:
- if your real test is soon and your goal score is where you want it to be, just start reviewing (see the last 2 articles linked above) and stop cycling through so many tests
- if your real test is soon and you goal score is substantially below where you want it to be, postpone your real test
- if your real test is farther away (including the scenario in bullet 2), stop taking so many tests, so spend the next 2-3 weeks really digging into all the data that will help you to *get better* and then take another test several weeks from now. Don't look at any of the prior test questions in the meantime so that you forget them as much as possible.
Also, take a look at the How To Study section of this article; this is how you actually get better:http://www.manhattangmat.com/blog/index ... -the-gmat/