Depending on where you stay in Big Sand Lake, a free airport shuttle might be a round trip to and from the airport or it could be just a one-way shuttle to your hotel.
How often will the shuttle run?
It depends on the hotel you choose to stay in Big Sand Lake. A courtesy shuttle to and from the airport may run 24/7 or it could be restricted to certain times a day. Check the hotel's policy on Expedia before booking your stay.