I think it depends on the way your car has been treated. I've mostly avoided potholes and harsh bumps and what-not over the years. My suspension was fine at 113k before I replaced it with an H&R Cup Kit. Only changed it out because I wanted to, not out of necessity.
2005 M54 325i///Alpine White///UUC Lightweight Flywheel///UUC Evo3 w/DSSR///UUC TSE3///UUC Sway Barbarians///BMW Performance Strut Brace///H&R Sport Cup Kit///O.Z. Ultraleggera 18X8.5's///Predator Orion V2's///K&N CAI///Shark Injected, Mother approved.