You could always take it to a dealer unfamiliar with the car and have them do a check... or a trusted indy shop. Being it's a 128 there are less things to go wrong. Also, if you believe what you read here, everyone has problems but you have to remember there aren't too many of us who get on here to boast about how little hassle their cars give them. Most of us got here looking for a solution to a problem, we are enthusiasts, there are many more folks out there who bought their '28s and '35s and just drive them, paying no more attention to their awesomeness than they would to a Yaris. By far, the majority of people treat them (as Dack would say) as an 'appliance'. 9 out of every 10 people I meet at a gas pump and talk BMW have no idea what car they are even driving! Not just 328s but 750s, 550s, etc.
I put a few bux away each month for stuff that comes along - if I don't use it I'll upgrade something.
I think if these cars are left unmolested they can and will last a long time.
We do not inherit the Earth from our parents; we borrow it from our children