Have always bought new vehicles but we keep them forever. I've always done some spirited "ring seating" of acceleration then let the engine coast it self down with the throttle closed, repeat this process a few times. The I change the factory fill as soon as I get the vehicle home....15-50 miles typically. Then I change it again at 500 and then switch to normal 5k changes. Have never had any internal engine issues and have one at 170K, one at 158K, one at 150K and one at 110K. Not saying this is why I've had good luck but I don't see where it hurts to dump the initial break-in metals as soon as possible. It isn't up for debate about whether new engines produce elevated levels of metal in the oil.