Some folks perhaps are not much aware of the big gains in quality of most or at least many commercial motor oils. It was only a few years ago, that Cat recommended 10,000 mile oil changes on over the road trucks. I just retired from a national carrier, that used 30,000 miles as the target for oil changes, and used Rotella conventional. Trucks went 500,000 miles without one hiccup, they sold them and got new ones, but the engines never used oil or broke down.
Unless a person lives in Siberia, where synthetic oil helps start an ice berg of an engine, I would recommend to the occasional user of a tractor, (IE:--short use intervals, varied use, light duty use, likening the use to an around town car)---I like the idea of shorter drain intervals and normal conventional oil. Figure this, an over the road truck goes approximnately 50 miles an hour average, when stops and hills and towns are figured in. In 100 hours, the truck probably has only gone 5,000 miles. No trucking company on earth changes oil every 5K.
I just got a new 6330 John Deere, loaded cab tractor and loader. It's got 20 hours on it now. When I get it broke in, I plan to use Delo 400 Synthetic, and change it every spring. I will have some very cold winter time use in Kansas. There is 100 degree summer temps too. I suspect I might use the tractor 100 hours a year. But if the tractor worked hard every day, running many hours on end, I would let it go 200 hours and not worry. But if I used it 25 hours a year, I'd probably use the conventional Delo and still change it every spring.
I think some guys worry too much about condensation and sludge. Condensation burns out of oil pretty fast when it gets good and hot. It's not like a hose is dripping in the motor all day long. The oil can hold sludge and soot too, not all that much of it in 100 hours anyhow. That's my take, and my tractor cost a bundle, but I will not be changing oil every week due to worrying about sludge and condensation, or the oil failing. The Major companies have good products to do the job.