If the car is left stock and driven sensibly, it will last a long, long time. I have seen cars that went between 150k and 200k. Granted, not many turbos get driven daily, so this kind of mileage is rare.
Like any car, they are best not left sitting for months on end, they need to be properly warmed up before being driven hard and they are NOT drag cars. Think of it this way; warm them up thoroughly, use them as originally intended, to get from point A to point B quickly (a fair distance here, not just a squirt up through the gears for half a mile) and cool them down slowly before parking.
I've seen idiots hammer them through the gears within a minute of starting them. I've also seen people jack up the boost and destroy them from detonation. That can happen quicker than most people can hear the knocking and react to it. These are the cars that get rebuilt before 100k.
Maintenance is important. Aside from the routine stuff that's in the owner's manual, they need to be looked after by somebody that is familiar with the 930. You need to keep an eye out for intake leaks and other things like that. These cars are getting old now, so pulling the engine for a service allows you to take care of a lot of little things that deteriorate slowly over time.