We have the buried fence for our dog. We trained her on it at about 4 mos old and she was great-only got out once or twice that first year and that was it. BUT this year at around 4.5 yrs old, she suddenly went over the boundary-probably was chasing a critter of some kind. We had no idea she would do it-she had never even tried before other than the couple of times at the very beginning. She got hit by a car on the highway and thankfully, is fine now, but it was scary. She stayed at the vet for about 4 days and at first, we weren't sure if she would live. Now she is confined to the part of the yard with a regular fence and goes out (still with the radio collar on) only if we're right there to keep an eye on her. Luckily we have a big fenced yard but she gets bored because she used to have 10 acres to explore in. Now it might be about half an acre.