5,000 miles would be fine. It's still on the conservative side. If you truly want to know how long to extend, then get an oil analysis done. They will help you dial in the perfect change interval based on your driving habits and your particular car. If you don't feel like spending the time and money on an analysis, a conservative 5,000 mile interval will be more than adequate.
If you want to get an analysis check out Blackstone Labs.
Blackstone Laboratories - Gas Engines