I’ve owned my 91 348tb for 13 years. I’ve put on just under 21,000 miles. About 1615 per year I guess.
~5500 miles in 12.5 yrs in my GTS 6 spd. Special occasion car, minimal highway miles, and always had other interesting cars to drive. I also compete 4-7 weekends in NASA German touring or BMW CCA race series.