I know that a lot of people are curious about this, so I thought I would post my partial experience - I took and passed SD (My last ARE) on 10/26/16. I received an email from NCARB today (12/21/16) that they had sent my record to CAB - almost 2 months later. I had already completed IDP more than a year ago, and I hassled and called NCARB at least once a week (maybe this didn't actually help my cause ). I'm a totally normal candidate with no special circumstances.
I'm still waiting on my letter of authorization - although CAB assured me that it should be no more than a couple weeks before I am authorized.
I'm sharing this information in light of the 03/01/17 exam change - it is definitely possible that you may not be authorized before that date if you are taking your last exams right around now.