We've had it take (from the time we got off the plane and onto the concourse to check in at the resort) as little as 45 min and as much as 2 hours and 15 min.
It will all depend on a)how busy the airport is and b) how many stops your ME bus will take and where you are on that list of stops.
The 45 min duration was in mid-January (aka SLOW season), there was almost no line at airport check in, and the Contemp was the first bus stop.
The 2 hour and 15 min duration was in mid June, the airport was nuts, check in at the airport took almost an hour, and I was the 2nd to last Bus Stop.