That’s a similar question I have. We now have our second Great Pyrenees puppy. We got our first at 8 weeks. She was crazy wild until 18 months. I had read that a vet remarked that Mother Nature “flips the switch” on this breed at 18 months and they become calm, sedate dogs. Our first did exactly that. Many of her obnoxious behaviors suddenly ceased. By age 2 she was the most calm dog, ceased digging trash out of the trash cans when we were gone and was completely well behaved wherever we go, outdoor cafes, hiking on trails where other dogs pass us by. Our second Pyr is now almost a year and we are so ready for him to get to the 18 month mark. He has many of the same behaviors she had – zooming around and digging 2 foot hole in 2 seconds. I’m curious if there have been any studies to this behavior. Since they are usually working with a flock from age 7 months, I’m not sure why the “calming” occurs. Our 4 year old was spayed at 7 months, so I don’t see that as having an effect. Our vet wants us to wait until age 2 for our boy since he is to be very large (160lbs) and he feels he needs his hormones for bone maturity. So it will be interesting to see if he calms at 18 months. He is having fewer bursts of energy behaviors per day, so perhaps he is on his way. We saw his 5 year old father, who was as calm and gentle as you could ask – off leash and truly remarkable.