I gotta side with the Ninjas on this one. In my opinion, you should only do a practice exam if you're about to take your first exam section, just so you get a feel for what to expect (time constraint, format, exhaustion factor, etc…). But once you've taken one section or one practice exam, ditch that for the rest of your sections. You're not learning, and no score you receive on the practice exam is really worth counting on. Either you score low and it kills your confidence, or you score high and it makes you complacent. Either way, you're in worse shape than you were before you looked at your practice exam score.
Don't take them for the score. Don't even take them to find out what areas you're weak in (just hammering MCQs can tell you). Just devote your time to STUDYING.
AUD - 79
BEC - 88
REG - 87
FAR - 86 - Woot, all done!
Ethics - 100