I've got an '03 330Ci on 78k miles.

It uses oil, but nothing horrendous. The engine is a peach, and rightly deserves the acclaim that it's such a smooth engine.

Look carefully at rear tyre wear and note anything out of the ordinary.

Check that the top end of the engine doesn't rattle excessively.

At 40k miles, it'll still be like new. I doubt you'd have any problems for a considerable length of time.