I had a pretty bad experience with exhaust studs - the front ones on my bike got eroded by heat & salt so I took it to this guy who got one out by welding a nut onto the stud and turning it out, I think he used an induction tool on it too, but he couldn't get at the other one, in the end he welded half a stud onto the broken one in place, but that too eroded away, faster than ever, I think it was just a normal bolt, rather than a more heat proof purpose made stud.
Anyhow, at that point he told me to take the head off and send it off to be spark eroded, this would melt out the steel leaving the aluminium intact - didn't turn out that way, when it came back from the spark erosion guy, it had been re-drilled and helicoiled - I wasn't pleased - I hadn't wanted a helicoil - did they even spark erode it as requested or just drill it out? Don't know for sure, but it was a disaster, the helicoil wound itself out every time I took the exhaust off, after about 3 years I threw the towel in and got another used head off eBay, just so I could say goodbye to the helicoils.
My rear cylinder studs are pretty shoddy, gonna have to tackle them sooner or later, but as long as it holds, I'm not keen.
Last time I checked, my front studs are still pretty good, probably cos we had mild winters lately with less salt on the roads. I didn't use any thread locker and was pleased to be still able to move one of them with 2 nuts in place a few months ago, I have a spare pair of OEM studs ready.
Its the front I need to watch, as that's where the salt gets in, the rear one has a fracture and a bit of thread mangled, but it holds for now.
When I googled it (maniacally) people told me to get a good welder to weld a nut on and turn them out easy to do etc, etc, it wasn't that easy in my experience. For years I thought maybe my tech was no good, or the spark erosion process not what it was cranked up to be, but like I said, I'm not even sure they even attempted spark erosion, I had an airscrew stuck in my throttle bodies, took it to this guy who was going to spark erode it out for £25, I thought great! When I got there, he said no need, can drill it out easy! He then proceeded to wreck my throttle body - had to replace that too!