There is no ironclad rule to lighting, each scene has it's own unique settings and requires close attention to mesh and material content.  Too many lights can bog down your system.  However, high poly meshes, in combination with hires textures, can do just as much rendering damage with just one infinite light present.  So, the bottom line, consider each scene carefully and don't shoot for the moon by maximizing your settings.  You will need to strike a compromise somewhere to achieve the render you are after.