DME has a pretty good idea how many guests are arriving at that time of night. If they are expecting, say, 12 people between 1 and 2am, they are most likely going to try tiger all 12 in the same bus. If the resorts are really spread out, they might put two buses out, or even vans.
Some people have had really quick service at this time...short wait for the bus, then departing after a short wait....getting them to their resort about 60-75 mins after landing. Others have had much longer wait times....taking over 2 hrs to get to the resort.
There's no way to tell.