Them old dogs know!We adopted a 5 month old lab in November and purchased the Halo 5 for her. It only took a couple days of training and 1 or 2 zaps from the collar for her to learn real fast where her boundary is. We don't even have the prongs on the collar anymore because the beeping the collar does if she gets to close to the boundary is enough for her to return. I may need to put it on the 8 year old lab for awhile to remind her as lately she's been testing what she knows is her boundary.