Oil changes are determined by the FSS in which the default starts at 7000 mile service intervals. If you don't drive with your foot crammed to the floor you'll actually gain additional mileage as you go. If you drive in stop and go traffic or "drive it like you stole it' you can lose mileage. I average around 8K on my changes.

I change when there's a couple of hundred miles to go on the FSS.

Synthetic oil is too expensive to waste.

Make sure you use a quality fleece filter. I use MANN filters. You can search for them and generally buy several of them for a discounted price.