I now run 5,000 mile 1 year OCI's on my 2002 F150 4.6. My drive to work is 10+ miles each way and an occasional longer trip. I'm in northern NJ, with all 4 seasons with winter being too long. My oil always comes out dark amber. I know that is not conclusive but I've always changed the oil at 5,000 miles max, usually about 6 months in the past but no more than 1 year. The oil is Motorcraft 5W-20 Blend and I use a Motorcraft FL820S oil filter. This has been since new. My truck will rust out before the engine fails internally from lack of oil changes. I only do 5,000 miles a year because I have another vehicle that I also use to go to work in the "good" weather.
Whimsey