We flew down in March on SW and I did not buy EBCI. It was a full planes and we were the third stop of the day. We were A36 & A37, but the plane was pretty full when we got on. We were able to sit together in the exit row as we fit the criteria. I would have hated to be much further behind or I think we would have been split up.
Coming home we were A20 & A21. We were in row 6 next to each other. It was a 6pm flight, but obviously most people, if not alll, got off in Orlando.
Both times I checked in with my smart phone right at 24 hours. Keep in mind it was just DH and me, so we did not have to sit together. That is why I did not buy EBCI.