My 1993 Nissan (built in mid 92) went to its grave with its original exhaust system intact, 30 years old and over 400k miles. That car saw all sorts of salt over the years. All the cars I owned when I started driving in the early 80's had multiple exhausts over their lifetimes.
Many more exhausts lasting longer than they did in decades past, I think we can probably attribute a lot of that not only to more OEM's using stainless pipes and mufflers, but also to only having unleaded fuels now, as well as the decrease in sulfur in todays gas. Leaded fuels had perchloroethylene, bromine, and whatever else to help prevent lead deposits, but those same additives had a nasty habit of combining with the water in the exhaust to produce acids and the pipes got eaten from the inside out.