Just took apart my 10 year old Ford, with plated steel nuts on hardened studs. Had to heat things up with the torch to get it apart after 370,000 miles. I rethreaded and installed new nuts, had the bolts been new as well instead of slightly worn originals I might have used some never seez. �The new nuts were a loose fit so I didn't do it.
Pretty much anything used in that application will eventually rust up and seize up. If it is a nut and bolt it is no big deal to break or torch it off, but a stud is a different matter. Use brass nuts like Nate said on the stud if you can..I would prefer a stud with a brass nut over a bolt threaded in tight, as chances are that bolt WILL break upon removal like yours.