12 years ago I got my lovely girl from a rescue centre. She was 3 at the time (or so they said) and had had a number of different homes, all of which had given up on her as she was aggressive.
She was a bit of a pain, but was the sweetest and kindest dog i've ever met when inside the house, never a growl, a grumble or any kind of dominant behaviour. We muzzled her when out, flooded her with love, and she was soon "cured" of any aggresive behaviour (though it took time).
She is a black lab cross whippet - though slightly rounder in her old age 
She is now well over 15, and has just been diagnosed with heart failure :( she is on a cocktail of different medications (stared yesterday) after a dramatic collapse.
I lost my dad earlier this year, and am heavily pregnant with DC2. I don't want my lovely doggy friend to die :( She's been with me longer than I have been with DH!
Logically I know she can'tlive forever, but emotionally it hurts :(
Has anyone been through this? And how long did your dogs last after diagnosis? The vet can't/won't give me any kind of timescale.