I'm sorry you are having to face this - I've had to help 7 Cavaliers to leave this life, one the decision was taken for us by the vet during surgery, but the others we had to decide. I ALWAYS feel it's better to let them go too soon than to leave them too long, as Margaret says above, sadly many people keep dogs going too long and then do carry that guilt. My own vet said that was one of the hardest parts of her job, so many times she would know that an animal had had enough, but the owner insisted on keeping them going.
I don't believe my dogs let me know,
I knew, from knowing my dogs intimately, when what they were dealing with was just too overwhelming for them and nothing further could be done to help them. One of them was only 3, another was my heart dog who was only 6 - age is NOT a deciding factor sadly, we would all like to have Cavaliers who live well into their teens but the reality now, due to all the health problems they suffer from, is that long lived Cavaliers are rare.
With Cavaliers, they wag their tails until they leave us, so I don't think that is an indicator - even a dog in severe pain, as they want to please us and they are genuinely happy to see us.
Also, especially if they are on steroids, SM affected dogs still tend to have a good appetite [obviously not in MVD or Pancreatitis, kidney or liver diseases etc]
PLEASE read this section
http://www.cavaliertalk.com/forums/...-you-know-when-it-s-time-The-hardest-decision
Dogs also have no mindset for emotional surrender or giving up. They have no awareness of the inevitability of death as we do and they have no fear of it. It is fear that so often influences and aggravates our perceptions when we are sick or dying and it becomes impossible to separate the fear out from the actual illness after a while. But that's not the case with dogs. Whatever we observe to be wrong with our sick dogs, it's all illness. And we don't even see the full impact of that until it's at a very advanced point, because it's a dog's nature to endure and to sustain the norm at all costs.
If that includes pain, then that's the way it is. Unlike us, they have never learned that letting pain show, or reporting on it, may generate relief or aid. So they endure, assuming in their deepest doggy subconscious that whatever we abide for them is what is to be abided. If there is a "look in the eye", or an indication of giving up, that we think we see from our beloved dogs, it isn't a conscious attitude on their part or a decision to communicate something to us. It's just an indication of how tired and depleted they are. But they don't know there's any option other than struggling on, so that's what they do.
We must assume that the discomfort we see is much less than the discomfort they really feel. And we do know of other options and it is entirely our obligation to always offer them the best option for that moment, be it further intervention, or none, or the gift of rest.
THE MOST IMPORTANT CONSIDERATION IS:
IS YOUR DOG HAPPY WITH THEIR QUALITY OF LIFE?
Are they able to comfortably take themselves outside to eliminate - dogs who are house trained can find it distressing to soil in the house.
Are they able to interact with you and their companions?
Are they able to rest comfortably? Enjoying their meals?
You can add to this list with things you know are important to your own dog.
I'm sorry you are dealing with this and I do hope that Abbey will be more comfortable on the higher dose of steroids.