Originally Posted by trader4

I would disagree. IMO, if you have an original BMW alternator and it's
working, I'd leave it alone. If you replace it with a brand new one
from Bosch or Valeo, it's expensive. And if you replace it with a $200
rebuilt one that you buy from the typical channels, you're depending
on the quality of the rebuild, which is done by some volume, low cost
vendor in Mexico or similar. They take in cores, quick test them, and
in many cases, only replace what tests bad. The core you send back
is working, it's unlikely they are going to replace the VR for example.
The next guy winds up with your old VR. If you take out your working
alternator and replace it with a rebuilt, that next guy is you.
.

Fuel filter, sure that should be changed. But fuel pump, again, I would
not screw around with what is working.

All in all, I don't buy into a lot of the preemptive replacement of parts
that in many cars, last the lifetime of the car.