Uncoated headers aren't going to disintegrate and fall apart in a year or two. I suspect there are people here that have had uncoated headers for 5 years or so, and they are still functional. Beyond that, you may be on borrowed time. Just a guess.

I have a set of coated AS&M's that I bought used, 6 years ago. The guy I bought them from used them for 2 years before that. At the ripe old age of 8 years, they are showing signs of rust, mainly at the main flanges, where the weld spatter seems to be the starting point for small rust bubbles. The AS&M's have taken a "thermal" beating though, having spent their entire life on 800HP blown or nitrous engines.

 

Thanks, Fred. I think that gives me a pretty good idea