Headers on my 70 Buick 455 have been in place for 17 years !!!! I wouldn't believe it either if someone told me that, but it is true. I have taken them off a couple times during that time though, here's what I do.

Sandblast thoroughly, be sure you get around all welds.
Hang and blow off then wipe entire header with laquer thinner to remove any residue, do not touch the outside surface with your hands.
Paint with "VHT" brand header paint.
Use care when installing to not scratch the paint off.

That's it, granted the car sits inside and is only driven on weekends, etc, but that in itself can be more detremental than driving often, which keeps them dried out inside.
These are not ceramic coated or powder coated, just done as I described above and they have been on the car since 1996 (knock on wood!).
Jess