Matt's absolutely right, Joel.  Cast iron is a wonderful carrier of heat.  That's why we use it in restaurants for sizzle platters and blackening.  We get them scorching hot.  For home use, unless that's what you intend, you don't want your pan any more heated than the heat you intend to cook with.

In most pans once you put product in the pan, the temperature drops.  Cast iron isn't quite like that.  It's build up of heat will sustain it through the introduction of food.