I have 2300 miles on my stock exhaust, and other than a gold ring around it from heat damage to the chrome. I did have one of the nuts that hold the header to the cylinder head come loose, I caught it before it completely fell off. While working on that, I discovered that both studs would unscrew from the head by hand. I completely removed the header pipe (leaving the silencer in place) double nutted the studs, and snugged them up a little more, then removed the nuts, and reinstalled the header pipe, using the original gasket, just snugging up the nuts. That was 1500 miles ago, and they have not come loose again. I cannot hear a leak at the head, and there is no carbon buildup on the header.
You have to be really careful with those studs. The head is aluminum, and while the studs are steel, they are very soft steel. Being an auto mechanic, I have developed a good feel for how tight things should be. Be careful using a torque wrench. It sounds like a good idea, but the amount of torque required is so little it would take a very accurate (expensive) wrench to measure it correctly. Many people have broken off bolts while using a torque wrench (including myself)
At some point in the future I plan to get some stronger steel studs that are longer than stock, and safety wire them in place.