Don't buy it; everyone knows that Triumph doesn't know yet how to make bikes that last more than a couple of years. 110+ years experience is nowhere near enough.
I've owned 3 Hinkley Triumphs and my experience is about 40k miles is when they start getting broke in good. They start shifting smoother. My '05experience has just over 76k miles.
Remember...this isn't your typical motorcycle engine...think of it more as a car with 2 wheels . As a matter of fact my son's car has a 1.8L engine and I would reasonably assume that he could get 100k miles out of his little 4 banger. No reason to assume that I would get any less out f the Rocket
Ian has over 100,000 miles on his 2006 classic Pretty much shows that properly taken care of they last. I beat the snot out of mine and have over 60,000 miles ButI have had to repair things I damaged not Triumphs fault