The small band of hunters must return to their tribe, or else they will perish, and their tribe will be severely weakened by the reduction of their number. The tribe suffers in two ways, for the hunters are their primary defense, as well as the procurer of highly important protein for the diet. The mission, much like the group itself, is there for a reason. Should the mission become more important than the purpose, such that the mission be sustained long past any reasonable expectation that projected outcomes be met, it becomes a self-defeating exercise.
Of course, we have returned, and I am very interested in the question of how to explain the working of the Holy Spirit to children. I've just looked up Piaget again, and I think I have the beginnings of an idea.