I think we don't have enough empirical data but a lot of theories and maybe some reasonable wishful thinking. I want to keep mine to 200k+ too. Now at 10k and about to invest some suspension upgrade bucks.
1. It may help if you got the EGR recall done at a lower mileage point. I got mine done around 5k.
2. It may help if you drive the car hard and/or at mostly highway+ speeds.
3, It may help if you use good quality fuel.
4. It may help if you use a good fuel additive.
5. It may help to get a walnut shells blasting every 40-50k miles.
Any other ideas.
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 Michelin PSS tires (winter OEM 17" wheels and Blizzak LM-25).