If you're on dirt roads a lot, change your oil filter (with a Fram Ultra, good to 80% 5 microns, spanks the Toy OEM filter....) every 5,000 miles.
Otherwise, a Fram Ultra easily does 10,000 miles, and they say it will do 20,000 miles, but I'd cut it off at no more than 15k miles just to be sure.
I just noticed the "southern AZ" location for this. Certainly make sure your air filter air path is tightly sealed, but that is a place I'd definitely want a Fram Ultra, holds more dirt, change it at 10k miles in that dusty Mad Max style s. AZ desert dusty area.