Do an Engine Oil Analysis. (EOA)
Blackstone Labs
That will tell you what you need to know. Its not expensive and its a good way of tracking your engine's condition too. It will tell you if you can wait longer or need to do more frequent changes.
Oil is a tricky thing hence why there is always so much discussion on it. Your driving habits, region, engine, and oil all have an effect on your oil's performance.
For me I change my oil once per year. But I barely drive the Z 3000miles a year. And my EOA said I could have used the oil even longer.
Also when looking at change intervals its not only engineering at work its management and making money factoring in. More people will buy an oil if it says 7500mile changes then one that says 3000. And good luck getting an oil company to replace your engine if it fails. Same goes with maintenance schedules is it better for you to come in and drop $100 every 3000miles or every 7500. And Nissan is on the hook for replacing your engine if it fails and they are doing the scheduled maintenance.