I see lots of posts regarding wonderful new exhaust systems, obviously people upgrade for performance, looks, and sound.

Besides those reasons, do people upgrade simply because their stock exhaust rusted out? I'm curious, does my '08 MCS come with a stainless exhaust system that will last indefinitely or will it go eventually? If thats the case, if replaced with a stainless unit (JCW or equivalent) should that last the life of the car?