Personally, even out of warranty, I would change the oil once a year regardless of mileage. My reasoning is that over the years, the mileage interval for oil changes has gotten longer, most likely due to improvements in the engines and improvements with the oils themselves. I went from 3k to 5k to 7.5k intervals as I moved to newer cars, with updated engines, but if I remember correctly, the time interval hasn't changed, regardless of the engine age, the number of cylinders, or the age of the vehicle. It's always been every 6 months, or every 12 months. That recommendation appears to be the same for almost every manufacturer, regardless of the oil's weight/viscosity rating.
Most sources claim that engine oil degrades over time, collecting contaminants and in some cases collecting moisture from temperature swings. I would be inclined to trust that and change the oil accordingly, but if you wanted to, you could take an engine oil sample and send it in to a lab for a used oil analysis. They would be able to provide a recommendation based on the actual data from your specific use case, environment, and driving habits.. but then the cost/time spent collecting the oil and mailing it in may cost almost as much as an oil change, so it may not be worth it unless you don't see your use case changing in the next few years.