How can you tell a dog is going to die?

Unfortunatly my vet said that when a dog is nearing the end of their life a bunch of things start to occur all a once w/ the dog. My dog is 14 years old and I have had her half my life. Recently I noticed that she had dropped a bunch of weight. To the point that her ribs were showing. Upon noticing this I checked her teeth and realized her teeth were all broken and decaying. Thus, she could not chew the hard dog food that is given to my dogs daily. Then she started not being able to hold her bladder. She was a dog that never went to the bathroom in the house to urinating in her sleep on her bed. Then about 3 weeks ago she was following me around the house and upon further inspection I noticed that her eyes were closed and one eye seemed to be very swollen. Found out from the vet that she had had glacouma due to her cataracts and sometime stress and age can cause glacouma to flare up and a lot of fluid will enter the eye and not exit causing it to swell. Once a dogs eye swells, they will most likely be blind in that eye if you do get the swelling down. So, this is when the vet explained to me that her having all these symptoms and problems meant that she was nearing the end of her life. He said that when dogs get close they go hard and fast and things snowball w/ them. But, luckily w/ a diet of boiled chicken and canned dog food I was able to bring her weight back up. Older dogs lack protein and the boiled chicken provides this. She is now almost back to her normal weight, the swelling in her eye went down and I am proud to say she is still here w/ us. I have to deal w/ her bladder problem, but that is worth it to me to still have her by my side. Pay close attention to your senior dog so you can recognize symptoms the minute they appear and can do something about it. If you don't pay attention then you could lose them sooner than they could have lived. I now check her everyday and she always comes looking for me at feeding time because she knows she gets the "good" stuff at dinner time. But, remember, if your dog is still eating they are not in any pain. Alot of people put their dogs down before they really need to be. My vet says that as long as they eat everyday they are fine to still be here.