Yes they certainly have been, mine are 15 years old but only 72k miles. Exhaust's like to be hot all the time and cold/hot/cycle on very short journey's soon rot them out (from inside to the outside) due to the amount of water made with each galleon/litre of fuel burnt. Believe they are 419 stainless which is the absolute minimum with 316 the better bet for one owner cars.
If I manage to get a MGR set then another 15 years will see me out ;-(
Kev