Better option performance wise yes, longevity wise meh no not really as far as header vs manifold... old school cast iron headers can match manifolds in durability but i believe only ford makes cast iron headers now days (i could be wrong here.) but a manifold is cast iron and durable as all hell and almost never warps at the cost of restrictive flow of course. shoot manifolds go 20+ years without warping to the point of a leak all the time lol a stainless header isnt doing that. stainless headers warping over time especially on a DD is a common issue (of course heres a part where quality of product comes into play.) but obviously provide better flow and performance then stock manifold.
As far as the bolts go they break because of continuous expanding and shrinking of the metals from duty cycles. aluminum heads increases the wear during these "duty cycles" on the bolts. for a while the bolts will expand and shrink with the manifold but eventually fall behind and being stressed to the point of breaking. This is still going to happen with headers, and the bolts can still break over time. Its most common on engines with aluminum heads. A quality header bolt kit will hold up and possibly outlive OEM, but by no means can prevent themselves from breaking. i have seen/heard of multiple quality header bolts broken however