I bought my BMW at 30k and now has nearly 200k on the clock. (1997)

I like most BMW drivers drive the car it should at weekends; during the rest of the week its all careful motorway driving. In my experience I would say the bad points would be the paintwork, although I have seen a lot of good example and I wash it about once a month I would expect this to be better than it is. On a good note I am surprised how everything else is as tough as it is - Exhaust, battery, all suspension parts, rear shock absorbers used to be parts which needed changing at certain intervals but they are all original on my car. 

I would say to make a BMW outlast the owner is to make sure the cooling system always works as it should which means replacing the radiator, cap and coolant change when needed. The engine is designed to work at higher than normal temperatures for efficiency and performance - increased pressure means increased temperatures putting pressure on the radiator. If you ever come across a seller selling a BMW with an engine replacement or cracked cylinder head at some point and I would say that this is usually down to an owner that doesnt look after the car's fluids.

If I was looking to buy a second hand BMW I would look for oil changes being the top of the list. The least amount of owners is important as you can meet the seller and works out that he is a careful owner by his character but the other three may not be the same. Ideally a full BMW history, these may not be genuine but you can ring the dealer in the stamp book to verify.