About a year ago, I had a waitlist fill in under 20 minutes. It was during the first week of December, even.
Back in 2016, I needed a last minute (under 60 days) 5 night stay in mid October. Found one night at Poly, right in the middle of my needed dates. Booked it and set up two waitlists, each for 1 night either side of that date. Within an hour, one had filled. This was back when the wait list disappeared from your dashboard and you could call in and have MS complete the booking. Got that booking completed and set up another wait list for the fourth day. 20 minutes later, that wait list came through. Rinse, repeat. All four of the wait lists I set up for those single days filled within 3 hours of starting the search.
Steve