Keep in mind that it is the temperature at the GRATE that determines a good sear and most of that temperature is transmitted via radiant energy and flame, NOT surrounding cooker temperature. Infra-red grills prove this point.

When eggers heat their unit up to 500+ degrees, and read temps at the dome thermometer, they are heating the ceramic up far more than is needed to sear a steak for a few minutes. They risk frying a felt gasket that was never designed for such high temperatures.

Charcoal burns at a consistent temperature and has a maximum threshold of radiant energy it can put out. Heating the surrounding ceramic isn't going to increase the radiant energy from the coals much, if at all, but it WILL lead to fried gaskets and broken fireboxes.

If you want a good sear, keep the lump level low (to protect the gasket), leave the top open for maximum oxygen, and place the steaks as close to the fire as possible. Distance from the coals matters FAR MORE than dome temperature. Then close the lid to reduce flare up and wait the requisite 2-4 minutes. This will give you maximum radiant energy while keeping the ceramic as cool as possible.