I read that its the genes, when cavs were first bred using toy spaniels and flat faced lapdogs, the genes controlling the size of the brain and the genes controlling the skull size are from different types of dogs and dont correspond, there for is some dogs the skull grows to the lap dog size and the brain grows to the spaniel size causing problems. Some cavaliers have the same size brain as bigger spaniels but not the same size skull. I think its only a therory but makes sense.
What's the difference between a new husband and a new dog? After a year, the dog is still excited to see you.