We were just talking about this the other day. DH has a brown kelpie sheepdog who would be about 16-17yo and she has come really close to not making it a few times, but MIL gives her a dose of rawleighs tonic and it picks her up again. She doesn't live with us as she never got along with the Kelpie I have, who is a black kelpie sheepdog and they are bigger and tend to be more dominant personalities, so she stayed at the IL's. She hasn't 'worked' in the sheepyeards for about 2-3 years now because she just couldn't jump the fences and lost her speed so she wasn't able to move the sheep like she used to. She just sits around under the tree in the backyard or in her bed in the laundry now and to watch her move around really is like watching an old person walk, really crotchety and unsteady and you half expect her to just fall over because her balance is starting to go too. I honestly don't know what DH would do if the time came where it just got too much and she would have to be put down. He loves her dearly. My dog on the other hand is 11yo and she is slowly starting to show her age. She is greying around the muzzle and gets knocked up pretty quickly if she is working all day with the sheep but she still has a lot of life in her yet.