5000 mile changes is what I typically and historically have done.
SuperTech synthetic at Walmart is a bargain at $14.XX
Fram Ultra about $8, used twice.
So about $19 for a synthetic oil change every 5000 miles, that I can do in my driveway in 10 minutes, and is done right.
Not a bad way to go. Plus, its easy to keep track of. Just change the oil at 35,000, then again at 40,000.