My Tacoma and other dedicated trail rigs get oil changes at 3500/4000 miles, depending at times on what I mightve run them through. But there exclusively operated with long idle times, high RPMs, and in very dusty conditions so I figure them to be in the worst enviroment.
For my older vehicles I do oil changes, on our 3 new vehicles the selling dealer threw in a maintenance package covering all 3 vehicles ay the time we bought our last vehicle (2 months ago) so they go to the dealer.