hi jenny it seems that you have had a lot of bad luck with your dogs. i am on my third dog, the first one worked until she was eleven &a half. and then she had five years happy retirement. my second one retired at tenyears old. but she only had two years retirement before she got cansar. my third one is almost five, hope she will last a few more years. as she is a large dog weighing 38 kg. best wishes and the best of luck harold