On SDN, you'll find the rare few people who are verified and receive interview invites within 1-2 weeks. A more accurate average would probably be anywhere from 1-4 months after being marked complete

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My impression for a lot of schools is that those with the killer stats and apps get reviewed immediately, since all schools are like, "Aww hails yeah, we gotta swoop in on this before they accept their full ride to Harvard!!" These folks are all the ones who have like...6+ IIs even though it's only September.
I was complete at most schools early to mid August, but I've only heard back from 3 schools total. I would say I fall into the "in between" range of applicants (strong ECs, PS, and LoRs, decent GPA, but low MCAT), but it's only been a month of wait, so there's always still hope
Then there were those who had deficiencies or did not fulfill specific criteria and were immediately rejected following submission of payment + secondaries.
Supposedly there's those who are reviewed in "separate piles" if they full under SES disadvantaged, URM, a school's specific mission groups, are applying to specific programs, etc. You never really know, given all the variables
😀. Maybe if you haven't heard back from ANY schools (rejections, holds, etc.) by December, you should be a little concerned
😛