"As if he understands that no one wants an old, physically broken dog." ...
Every parent of a senior pet needs to read this.
A good sign your senior pet still has a good quality of life is if they're eating and drinking as normal. They should still be perking up at the sound of their kibble bag being opened for breakfast.
There is a particular kind of quiet magic in watching a pet grow old. The muzzle gone silver, the naps grown longer, the morning stretch a little more deliberate than it once was. Aging in companion ...