Well, I think I learned this the hard way in some respects.
Revolution GMAT 1: 580 (39 Q, 31 V) - took on Sept 11
Revolution GMAT 2: 640 (40 Q, 37 V) - took on Oct 9
Revolution GMAT 3: 670 (45 Q, 37 V) - took on Oct 16
GMAT Prep 1: 650 (44 Q, 35 V) - took on Oct 23
Revolution GMAT 4: 640 (48 Q, 31 V) - took on Oct 30
GMAT Prep 2: 620 (41Q, 35 V) - took on Nov 2
I'm not totally bummed out from a drop in my scores over the last two takes, because I scored a 48 in Q in the 4th Revolution Prep test. I began the 2nd GMATPrep test at 11 PM last night and it ended at almost 2 AM (and I did the AWA's). I did it to see how I'd do under "compromised circumstances." I didn't feel tired per se when I took the exam at the time, but I got 5 of 6 math problems wrong during the middle of the Q section (still having trouble with multiple factors of probability) and I had four straight wrong in the last 10 questions of the verbal section. When I saw those four questions I got wrong, I made some errors that I otherwise wouldn't have made, and I could have gotten a much nicer verbal score, even taking it while being tired. Though I never hit 700 on any single test yet, I still think I have that potential since I think the Revolution CAT scoring is decent and I did get a 48 in Q, and on V, I was doing really well before hitting four straight wrong answers at around questions 32-35 or so. Weirdest thing was that I didn't feel tired while taking the exam, but I felt it soon after.
Does anyone else notice a considerable drop in performance when taking a practice test right before bedtime, or past bedtime to be honest?