Your HPDE frequency sounds like mine. For OCI, I am sitting at 10K miles on the odometer, have been to one HPDE in Sept 2012, and have not done a single thing to the oil other than check the dipstick a couple of times. If I hadn't been under the weather and the garage being so cold, I would have changed my oil at about 5 or 6K. My old Jetta Diesel got a new jolt of Mobil 1 every 3000 miles for her entire time in my possession (20 years and 300K). I probably wouldn't go that extreme for sure with the 335d, but I would change it between dealer visits. That's just old school me. As far as I can tell, running around Summit Point one day a quarter or every other quarter isn't going to cause the car to break a sweat, not in my skill and league level. I only go on Saturdays and so that's four 10-12 minutes track sessions and one skid pad. The only thing that seemed to get beat up was my tires.
Mods-Etc: Quaife LSD w/VAC finned diff cover, M3 Rear SF Bushings, M3 sways & OEM Susp Front/Rear Cmpnt Kits ('cept strut brace), GC Caster/Camber Plates, AC Schnitzer M3 Sport Springs, JRZ RS1 dampers, JBD 100%, Goodrich SS brake lines, non-stggrd APEX ARC-8 18" wheels with Nitto Motivo tires (winter OEM 17" wheels and Blizzak LM-25).