I would plan on an hour. It is actually only a 30 min ride, but there is no way of telling what other stops the shuttle may make. I've usually been in a van for the ride back, so it took about 45 mins total. And, Mears will give you the time to be picked up...you tell them about what time you need to leave US/IoA and they will tell you what time the scheduled ride closest to your needs is leaving.