I recall going to a BMW owners rally with my brother and they were handing out million mile pins. There were 5 bikes and owners getting pins on this rally and a couple bikes looked like they went the distance whereas a couple looked like they were off the showroom floor...the thing that got me is the number of people who already had million mile pins..The boxer twin is an awesome engine. I can't believe I'm saying that since I used to laugh at them. But the 1200s are good and the 1250 is downright entertaining. I think the Boxer gets the weight so low that these bikes (RT, GS, GSA, RS) are just really fun and effortless to ride. With light parts and wheels, the Busa is a willing turner now too, but the 1250 is in another league.
I don't reckon there are too many bikes out there that can boast this sort of longevity.
I had a friend who had a Paris-Dakar GS1100 and boy he sure could ride that thing...he used to be a military dispatch rider when we still had them in the '80s.