https://www.youtube.com/watch?v=8FFQpFAU_SoThere is a teardown of a Duke IV after 50.000km on Youtube. Done by a Deutch magazine.
According to them the engine shows very little sign of wear, and as long as it's properly taken care of will last much longer.
In regards to max km I don't know.
I don't think 70,000km sounds much for the Duke at all.
What's the point of comparing a 690 single to a B-King? Kinda like saying a Toyota Corolla is more economical than a Lamborghini; it doesn't mean anything.I was "promised" 70'000km before the head needs to come off. So you can double that .....