On long haul trips, greater than 2 hours in length, Shotgun privileges should be divided equally amongst all passengers, as long as they are able to complete all Shotgun Responsibilities.
The Shotgun Rules have been designed around the shorter trip (less than 2 hours). For longer journeys, it is best not to use these rules because the incentives to be a Gaper are too great. Rather, you should divide Shotgun equally among those who want it.