On diesels according to BMW its 60K which is crazy I just use pipercross and clean it every 10k as its less wasteful then paper.
Its one open to a lot of opinion but IMO its better to either change regularly say 12months /10k or get something like pipercross and clean it regulary
If its due a service get them to read the car then are you using indy or dealers
Titanium Silver E90 LCI 320D M Sport Saloon
- Logic 7/ USB Connectity and Bluetooth/ Visibility Pack (Xenons, Adaptive Lights,Auto Wipers Lights and Corner Lights) / Sun Protection Glass/M Spoiler / Brake Ducts / BMW Performance Pack / BBS Wheels / SS Cat Back straight through with BCS Backbox