As I said before. I will follow that old school maintanence schedule by Mike Miller.
1. Belt tensioner-11287549588 $55,
2. Deflection pulley-11287549557 $27,
3. Belt tensioner for A/C-11287549589 $58
4. 2 fan belts.
I always replace the water pump and thermostat with BMW Coolant, fuel filter every 60K miles. I use RealOEM web site to get my parts #. Happy New Year.