Not knowing what brand and model plasma cutter you have makes it difficult to help! As a rule of thumb...if the nozzle orifice is no longer round...then you have lost energy density in the arc, and the cuts will not be as good as the torch manufacturer designed it for. That being said......on some plasma systems....the nozzle will get distorted on the first few feet of cut, while others will still be in good shape after hundreds of feet of cut.....that is due to differences in technology and design of the plasma system. Longer consumable life, which coincides with cut quality over the life of the consumables....generally comes with major brand plasma cutting systems.
Does the height control find the surface of the plate before each cut...then retracts to the (plasma torch) manufacturers pierce height before firing the torch? Does the torch follow the contours of the plate accurately during the cut while maintaing the manufacturers specs for cut height?