By the end of the summer, it may take 3+ weeks to get one's transcripts verified. You can minimize the effect of a later application by submitting to AMCAS at the time you take the MCAT (without knowing the score) to just one school, so that by the time the score is released a month later, verification is done and your Primary application is ready to send out to all additional schools (added when you know how competitive you are). Thus you'll get and complete Secondary invitations more quickly.