check out this video ............on oil changes

[StephenVA]

Oil services are always based on YOUR driving, weather conditions, dust level, hot cold cycles, length of trips, etc. I personally change my oil once a year (12-14 months) as total annual mileage is low and mostly short trips under 5-10 miles. My decision. Could the time intervals be longer? Cheap insurance in my view.

A potential solution to this question/tread might be Oil sample testing. As it is cheap and easy.

Blackstone labs in the US is a great option for low cost testing and insight into your BMW based on oil used, length of service left in the oil (additives). This service also provides great insight in to the engine condition. Especially useful for those who have just purchased a X5 and high mileage X5 examples where you would like to know more about what is going on internally.

Blackstone lab info:
Oil analysis is a quick, nondestructive way to gauge the health of an engine by looking at what's in the oil. People use oil analysis for different reasons: to see if there are any problems developing, to see if their oil is working well in the engine, and to see if they can run longer oil changes. Get started with your analysis by ordering a free test kit.

Blackstone Labs

While the sampling kit is free, the oil analysis costs $25.00.
Follow the link for more info....

Oh, and No I do not work there, I have only used the services and I have been happy with their customer service and feedback insight.