How often do you service your X5?

[kvc]

Prompted by another thread regarding oil level light and a picture of a motor with sludge and gunk in the oil valleys, I thought it may be interesting to discover how often forum members service their cars. I believe the original BMW suggested service interval was 15,000 miles or 25,000 kms when the X5 was first marketed(?) - who does it more or less frequently, and what is your reasoning behind this?
Please post a time or mileage / km frequency, with the type of oil/filter used and your car's mileage too. Do you use any additives (to deal with leaking valve stem seals maybe)? Perhaps we can learn something from the results?

I'll start by adding my details:

I service my car every 10,000 kms with Mobil1 0W 30 and genuine BMW filter. My car has 133,000 kms on odometer (owned since 112,000 kms) no additives except injector cleaner once every 4 or 5 fills at the fuel bowser. I've serviced all my vehicles at this frequency or more often (diesel motors) and have had no dramas with valves, seals or engines burning excessive amounts of oil (touch wood). The oldest vehicle in my 'stable' is a 1966 Valiant with a 225 c.i. slant 6 motor and 328,000 miles (original) that uses less than a cup of oil between changes (every 6000 miles).