Once a spirit is created, its lifetime will be eternal.  However, the development of the spirit is similar to that of humans, in that it experiences a stage of infancy. It knows nothing of its origin and has no experiential knowledge of, or predisposition toward good or bad. Its intelligence is in a state of potentiality, only beginning to unfold.  At this stage, the spirit acts in the material world, motivated largely by instinct, and in pursuit of physical survival.