More Good Days Than Bad
Add up the score for each category for the day. Remember, be honest. Having one bad day does not mean that they are done with this life. You are looking for many bad days in a row.
When the human-animal bond is no longer possible, when your pet is just not themselves anymore, and when the bad days start outweighing the good days, it might be time to discuss euthanasia with your veterinarian.
This is something we never want to discuss, but we owe it to our loved ones to not let them live on in pain. Keep in mind that it is better to euthanize a week too early than an hour too late.