Should I retake FL X?
I don't suggest it for a few reasons. First, your score will be inflated. This alone negates the predictive power of the test. If you don't need it to gauge where you are, fine, retake them. For instance, you could simply be going over the problems again to, as others have mentioned, understand the thinking behind it. However, if you are using it as a practice FL, don't.
One of the most important aspects of a FL is that it's material you've never seen before. It forces you to quickly analyze an unknown passage, tap into your knowledge, and answer questions you've never seen. If you knew exactly what was going to be on the test, it would take away from the somewhat frantic experience of getting that weird passage. It also makes you more relaxed overall because you know what's coming. Unfortunately, you will not have the luxury of either on the test. You will have to deal with weird passages. You will have to get out of your comfort zone of knowing what's ahead.
Then, you get into the timing issues which you MUST get down before the test. When you have prior knowledge of the material, you miss the chance at gaining more experience with the clock. Too many people underestimate the effect of the timer. Again, you have to get used to it and retaking problems won't help.
Think of the whole thing like sports practice. Sure, you go over some standard plays again and again to get a feel for them. However, to practice for a real game, you have a scrimmage match or an exhibition game. The other team doesn't tell you what plays they're going to run. If they did, it would eliminate the usefulness of the scrimmage or exhibition game.
