I had two that lived to 15+ each. All I can tell you is that I knew when it was time. I think that one day I realized that I was doing everything for them. Helping them outside to go, helping them to their food, wiping their backside when they would sit into the pile they just dropped using all their strength to push it out. They still live with me, even though HK has and will have my current heart until one of us passes.