It is never an easy decision. We had a fox terrier when I was a kid who lived to be 19 years old. He had catarcts and could not see the last several years. He had gone blind a couple years before the end. He knew when you put him on grass to go potty though and he was always happy to curl up with my sister whenever she was near him.
His decision for our family to have him put down was when he could no longer even attempt to stand. The vet thought he had a stroke or something like that and so we knew the time had come. Even on days he was weak before that he could stand even if he needed a little assistance, but it got to the point where she couldn't even hold him up really.
It is tough and I am sorry you have to go through this. I had to make the decision last year on a very young dog who I thought would be with me so much longer but cancer is cruel and doesn't care that she was so young. If the dog is not suffering I would let them continue to age and just enjoy every day you have with them still. If they are suffering though I think it is better to let them go. Your dog does not sound like they are in extreme pain, but only you will be able to judge that.
__________________  It's raining Yorkies here! LOL Teek  ,Rowan  , Raksha (Grand Puppy)  , Raelyn  |