150,000 miles is only 240,000Km . . Our first V had almost 200,000 km on it when we got it, and was a champ. After we sold it I very nearly bought a '97 that had 290,000 Km (180,000 miles) and it was in almost perfect shape too. Perfect compression, etc. I don't see why they shouldn't go way past 400,000 Km without major work, provided you get the valves adjusted regularly, and do the basic maintenance. They don't rust out like Toyotas. :-)
Hanging around here is a good start, since:
"engineers know the rules . . owners know the exceptions"