If you ask 10 people you will probably get 10 different opinions. I have one slatmill at the moment and it does about 4 turns with a good push. Thats about how i like them. You can probably do some adjustments to your mill to make it a bit more free spinning. Imo it's not as much about the spins as to get rid of vibrations. And most important use it with a bit of common sense. You can have the best mill in the world but if you overwork a dog it's pretty much useless.