I have taken DME back to the airport three times now, and it has not taken more than an hour from my resort (and that was bcs the driver had trouble loading my DS's wheelchair - apparently hadn't had much training on the lift). The longest was about an hour; we were picked up at BW (myslef and DS in wheelchair), fussed a bit loading him in, 4 more got on the bus, then off to POR, picked up 42 more, then off to airport.
I imagine if you have more than one other stop or you hit traffic it could take more than an hour, but in the three times we did it, it was under an hour.