I know about 10 people who wrote the MCAT in August at my school. I got a 36, my friend got a 34, and everyone else got between an 18 - 24. Every single person who got between 18 - 24 spent less than a month studying for the test. Most of them used their textbooks to study from, however, some used the Kaplan MCAT Comprehensive Review. My friend who got the 34 studied for three weeks before the test using ExamKrackers; he did one practice test. So, most averaged about a month of studying - a few hours a day - and except for my friend, who I guess is just naturally good at test taking, everyone didn't do so great. I studied my ass off though - four months, three or four hours a day, and a practice test almost every weekend. I did all the AAMC tests, I read the EK books over and over, and I used MCAT Audio Osmosis. I started off not knowing almost anything. Put in a lot of effort and you'll majorly boost your chances of scoring 30+, but you've got to work for it - don't look for a trend to give yourself false confidence, just study your ass off.
