With regular routine maintenance and replacement of parts as they wear out you should be able to get 300,000+ miles without many worries. If you have iDrive it might not make it that long, but no one knows. There are already numerous Bimmerfesters who have past the 150,000 mile mark. With maintenance and necessary parts replacements the motor is virtually indestructible.
Present - '06 E90 330i sport; Past - '04 E46 ZHP, '00 E46 328i
www.bmwcca.org member #388003 - Use me as a referral & you could win a one day ///M Driving School!!