In the Grand Scheme of things... you'll be saving yourself money if you just go by mileage. I would also say viscosity, but you really can't visually judge if the oils gotten thinned out by use, til ya drop-it anyway.
I always looked at the oil as "cheap insurance" that the engine will have the best chance to run well the longest.
Especially if you drive into the boonies for hunting, Man! You don't want to be worrying about "Gosh will the oil I currently have in there get me in and back out without taking a dump on me out in the middle of nowhere where the towing bill will be astronomical?"
Other thing I do.. force of habit from Motos... is always break-in new engines the same way I was shown for 2-Stroke dirtbikes. And always dump that first oil at 600miles.
I know some of the car manufacturers these days hook up their engines to machines at the factory to break them in. And that's all well and good, but I like knowing for sure proper break-in has happened. Where you push the engine pretty good, but don't wring it out, to ensure most thorough break-in possible. Big thing with breaking in a new engine is just don't be pushing it soo much that you're causing too much heat. That can cause scraping on piston which can pull some metal off the piston and stretch it over the opening the rings fit into, which would then affect how well the rings then seat from then on, messing up the seal for compression.
With todays cars just make sure you know if your particular car needs a certain kind of oil which has to have these various kinds of additives in it. Or NOT in it. (Usually not an issue unless a sport car).