depends on how you treat it and what you consider the "useful life" to be.
If you've got an automatic, it is somewhat likely that you'll have to replace the transmission within the next 50-60k miles.
Other than that, the engine will run forever (when treated correctly) and the cars are undercoated so rust shouldn't be a big issue. You might have to replace a VANOS unit at some point in time as well as a radiator or some other throw-away part, but that's about it, typically.
At 200k, I say that the car doesn't owe you anything anymore. At 250k, I'd probably be looking for my e46 replacement.