My one late night experience (arriving at 11pm) was not a good one. We were not standing at our resort's check in desk until 1am. We got right on the ME bus, but they we waited 20 minutes before we left. I really felt sorry for those people already on the bus. As our bad luck would have it, our resort was the 4th stop.
During the day I have had a huge variety in how the trips went. Sometimes we get on the bus and go, sometimes we have to wait 20 minutes before even getting on the bus. You really just don't know. Average time may be 90 minutes, but you have no way of knowing ahead of time if your trip will be average, or better, or worse.