you change your oil per the service manual that came with the vehicle. Also, I used to work at Ford and their warranty department would not pay for claims for oil consumption unless the engine used more than 1 quart per 1,000 miles. I have never used that much oil however.
I would recommend frequent oil changes only if you don't check your oil level; that is the reason I would tell people to change their oil often. People generally don't check their vehicle oil levels and if it gets changed every 3,000 or so then it is more likely to be caught before major engine damage if that makes any sense.