And don't forget they do those 'big battle' V-formations to save energy. Everyone except the leader is getting a bit of extra lift off the wingtip vortices of the one in echelon ahead. So apart from handing over the navigation, the leader is also taking a rest when he/she? hands over.
There was talk a while ago of transatlantic airliners doing the same thing to save fuel - ooer missus.
airsound