That's not the answer I was looking for. No one said I couldn't do more. The question should have been phrased, at what point should a person feel comfortable with their abilities to tackle such a challenge?
With the advent of Fat powder skis most any advanced intermediate looking to ski untracked pow pow can Heli or Cat ski. Just be honest about your abilities when booking and I'm sure they'll tell you if they have terrain that meets what you are looking for.