Now do the math. It averaged 33.3 mph.
That tells me a lot of idle time.
400000 miles in 5 years would ring another bell. Possibly a shop queen, caused by idling?
A friend of mine bought a T700 with a MX13 at around 1.2 mill km. It took him about 2 years to figure out the bugs. He likes it.
I myself run one of the most unwanted engines, a 2006 CAT C13. I like it. For me, there might be even a Paccar on the horizon.