No cohorts have been filled yet. We're still early. We are seeing reservations pick up quickly, but I'd be able to give you a more concrete estimate of fill velocity after about a week.
That said, we're planning to add a 7-day window: if a cohort doesn't fill within 7 days of your reservation, it cancels automatically and your card is released. We don't want anyone's payment method sitting in limbo indefinitely.