Power steering fluid does not need to be changed on any car until it really gets dirty, but it should be changed at that time. After all, it's a hydraulic system.
It's a shame about these reliability issue stories with newer BMWs because the V-8 M3 is truly one of the greatest driving cars ever made. On a track, it's up there with the all-time greats and plenty of fun in canyons as well. Amazingly great engineering from a driving perspective.