This was mentioned by Aaron in the forum on "Manifest psychic abilities and healing ". The exact quote was "When a person uses a psychic ability, they use phsycial energies with a connection to their inner capabilities. One should avoid using practies that involve the direct intentful manipulation channing of energies by means of will and volition. It had been said in the writings that the soul could only last one hour in the material world unguarded by the body. "
As no-one questioned this I thought maybe people knew what he was talking about.