From what I have seen, bimmers are pretty inconsistent.
Some BMW models/years are absolutely rock solid reliable with the capability to accumulate HUGE mileages over decades of hard use, while others are totally rubbish with electrical problems, fuel system leaks, and even wheel and rear-end bearing problems (which are virtually unknown on Japanese bikes). While I am sure it has happened, I personally have never seen or heard of a Gold Wing or Honda ST (or Suzuki GS850G or GS1000G for that matter) with a bad final drive bearing. Two of my vintage bike group friends have done transmission and/or rear end bearings on their bimmers.
One thing about the European brands which is consistent however, is that repair costs are through the roof. Parts are very expensive and often hard to get and finding knowledgeable mechanics for these bikes is too on these bikes. A broken BMW or Ducati is a hole into which you can pour money for a looooonnng time, according to my buddies that own them.
YMMV - but that has been my experience.
Pete
PS - despite all of the above, I STILL want a1978 BMW R100RS!!!!!