This subject comes up pretty often. There's lots of threads and posts about this. I'll summarize:
Oil has a maximum and a minimum operating temp. Minimum seems to be about 180*. But getting it closer to 200* seems to be better.
Oil is heated by rpm's. Extended high rpm's. Like 4000+ lap after lap. a 90 second autocross run or a 12 second drag strip won't heat the
oil to any remarkable amount. Unless you're road racing, you don't need an oil cooler.
Thermostats sort of work. When full closed, the route about 10% of the oil through the cooler. That allows all of the oil to warm up at the same time. When fully open, it bypasses about 10% of the oil back to the engine. That helps prevent pressure loss.
On a cool morning on the highway, your oil won't get close to 200*.