You are so right when you say once they start getting out it is almost impossible to stop them. We had a Great Pyrenees and American bulldog mix and she was about ten years old before she ever got out. When our other dog died she started getting out and we worked everyday trying to do anything we could to keep her in the fence. She ate through two by fours, she ate a hole in a chain link fence, my husband biult all our fences up to about seven foot high and she learned to climb over it. She was a good dog though. We think the coyotes were calling her out at night. She would come home bloody the next morning. One day we were grilling out and she jumped the fence and started pulling me by the shirt to the back yard and their was the nieghbors horse tangled up in their barb wire fence. She brought me back there to get the horse loose. We got her loose and she just nuzzled our Maggie may thanking her i think. She was a good dog. We miss that girl so much.