When our beagle was about 7 years old, we discovered that he had some renal/kidney issues. But he never seemed to be in discomfort. The vet at that time, did not tell us what to do, but gave us all the information we needed. Our beagle was given about a year to live. Maximum. Well, 7 years later, we had to put him down as his kidneys started to shut down. He had no bladder control. He wouldn't eat or drink. The fur stared to fall off his tail. We knew the day had come. But, with lots of TLC he lived much longer than the year the vet first said. We called a family meeting about two months before the day we put him down. Everybody said their goodbyes. It was hardest on me. My hubby and I bawled for a week and this dog had only come into his life for about three or four years. You have to do what's best for the dog.
If I can leave you with any advice, it's this: mark your calendar every morning and afternoon. Did your pet have a good, bad or up and down day? When the bad days out weigh the others, you know it's time. Good luck. Not easy.