How Close Should You Be to a Portrait Subject When Shooting With a 35mm Lens?

Many photographers swear by their 35mm lenses and almost never want to shoot with anything else. The reason for this is because it so closely simulates what the human eye sees and so it's easy for a photographer to go out there and shoot a scene just the way that they see it. That would be great, if 35mm lenses were absolutely perfect. While they've greatly improved, 35mm lenses are still not perfect and when used for portraiture still can't replace or do what a proper telephoto focal length can...