Kohler themselves state that oil should be changed every 25 hours of use MAX and more often if harsh conditions are present.
If I were you, I would use the non-detergent oil for about 5 hours and then dump it while it is still warm. From that point onward, go with STRAIGHT GRADE 30 weight detergent based oil and stick to the 25 hour oil change interval.
Installing an hour meter on your tractor will help you with that routine.
It really isn't fair to compare an MTD lawn tractor to a quality garden tractor such as a wheel horse. The Kohler K's are torque monsters compared to a vertical shaft B&S I/C engine. However, I fully understand your sentiment. :LOL