Our Golden Retriever, Libby, is 3 months old now. She's really growing fast! She is doing well with the training. We've taught her not to jump up on people, not to bite, etc. The only real problem we're having now is that she wants to chase the cats! So, I'm thinking it's time to get the wireless invisible fence I've been considering. I went to Menards and looked at one and it doesn't really say what age to start using it. It just said the dog needs to be old enough to be trained. What age have some of you folks started using one of these type fences?