Jim is right. With a QUALITY synthetic, the optimum mile change is about 7500-10K. miles.
The other issue is time. I would change the oil at least yearly or as Jim says, just before a winter sleep.
Having said that, I change the oil in my wife's Sub at 5K simply because she does tons of short trips. So, driving habits, like how hard you hammer your Box, is another factor to consider.
Cool topic.
More on
www.bobistheoilguy.com.