Merv, I have a 12 year old Cobra here with it's original exhaust system. It was only painted with high temp paint. No problems I can see with the exhaust and corrosion.
The headers were ceramic coated though and they are also still going strong.
Same deal with our last Cobra. It's also still going strong with just a high temp paint and is 11 years old now.
So ceramic coating the entire system will be more than adequate.
In my experience stainless systems sound different to mild steel systems. Although polished stainless headers look fantastic. But if you are looking for lower engine bay temps, then ceramic is the way to go.
The only thing I have seen that deteriates exhausts quickly is that heat wrap.