In my mind they let you know when they want to get out of this deal. It is often harder to do the right thing and I am sure in this case you did just that. Good for you.
I had a very loyal dog that I always thought would let me know when she was done. She had a lot of Titanium in her and was wracked with arthritis. I felt I saw the light go out of her eyes and that was when I decided that "she" had decided.
So sorry RoPo!!! Your story likewise made me cry. You definitely need to get Max back now (not that you didn't already), you need some serious cheering up.