Doug's Headers Hi Temp Black Coating Question

I have 2 set of doug headers. I have a set of coated ones on my 73 duster that has a 360. They've been on the car for maybe 5 years now and still look good. I have another set on my wife's Ford Falcon. They are the black painted ones. They have been on the car since 2015. The paint overall is holding up very well. The passenger side header still looks decent. We had a master cylinder leak on the driver side at one point so the paint is whiteish looking instead of black in those spots. The paint overall hasn't worn or flaked off. Both cars are drag only cars so they don't get driven on the road or out in the elements that much.