[Sid Squid]

As it's such a high miler it's a fair assumption it does long trips and probably many long days, where the engine gets and stays hot, as such it may have done no more - or perhaps even fewer - cold starts than the average 20,000 - 40,000 mile engine, for instance if you were to have a commute of 10 miles twice a day, that would be 10 cold starts for every 100 miles, your working week, but perhaps if you were a courier who did 100 miles per day, in the same working week you'd cold start half as often for 5 times the miles, as the great majority of engine wear occurs at cold starts before the oil is hot and the lubrication system is functioning correctly, used that way an engine would be living a much happier existence.
Bear in mind that the oil change at 'X' miles, assumes certain operating circumstances, an engine that has spent all of it's time at 70~80 mph in top gear on the motorway, may well have turned fewer revolutions in 6000 miles than a bike that spends all of it's time in town at 20 mph in 3rd gear has in 4000 miles.
Horses for courses, oil is still cheaper than bearings though.