What are you trying to accomplish? Are you trying to maximize the longevity of your engine or the longevity of your oil? They oppose each other, hard to do both. An oil change, in full synthetic, will be about $75. An engine change will be well north of $7,500.
Again, oil is cheap.
I plan to change my oil every 5-6,000 miles. Just like I did in my 2007 Eddie Bauer (traded in at 212,000 miles).
Most Owners actually operate their vehicles in "severe conditions", and don't even know it, like; short trips, city driving, idling, extreme cold, heat, humidity, just to name a few. This is murder on oil.
I do greater than 75% highway driving with very little stop & go.