I think everyone's experience with the NCLEX is a bit different.
I was (and still am) an older, second career student with three prior degrees including a masters. I've always done very well on standardized tests - nearly 1400 on the older, non-recentered SATs (95th percentile), top 10% on the GMATs, 99th on the TEAS, etc., all with either minimal or no prep (the guidance counselors at my high school were adamant that there was no way to prep for the SAT and any review course would be a waste of your parents money). For the NCLEX, I used my usual intensive, self-study, short duration rountine to prep (took a week off from work and did the Elsivier on-line review and the Silvestri book for maybe 6 - 8 hrs each day, with frequent breaks to jog or bicycle). When I got to the test - I'd scheduled it for late morning, expecting to be done in time for nice late lunch with a few celebratory adult beverages - I was stunned when the machine didn't shut off after question 75. No sweat, I figured, I guess I'm not as smart as I thought but surely the test would stop after a few more questions. At question 100, it got really weird. I started getting a lot of math questions, which are really my strong suit and even today, I'm certain I got those right. Long story short, 4 hours (of which at least 30 mins was bathroom break time due to my stop at Starbucks) and 265 questions later, the test finally stopped. I was now certain that I had messed up big time and on the way home, was already planning a new and different study routine for attempt number 2. I was so sure I'd messed up, I never bothered to check the state web site (they show you as having an active - or if you haven't passed, pending - nursing license within about 24 hours after you leave the PV test site. It was only after I started getting congratulatory calls and e-mails from friends and fellow students that I realized I passed.
Like I said, I think everyone's test is a different experience.