I was always very conservative on oil changes, but I now go 7-8K with synthetic. My Corvette has a oil change program based on miles, rpm, etc, and it would probably go over 10K but I never let it go that far. I change it myself so it is around 35 bucks with a good filter, so cost is not a factor. I give my oil to my buddy at his garage, and he burns it for heat. So really no waste.
