*HUGS*

I have nothing to add other than I'm terribly sorry. When my Aussie mix died last year my parents had been worried for 2 weeks that they were about to have to make that decision (I'd left her with them when I moved out for her happiness due to her age and affection for their other dogs). Then she got better for a week, but died in her sleep. Ultimately I'm glad she died after having been relatively happy about life for a few days rather than miserably declining, though I doubt very seriously I could have made "the decision" when she seemed to be improving.

There is no "wrong" answer, especially when you have a pet that's lived a long, full, happy life. Nala will help tell you when, and it's ok to let what you are feeling/can deal with best enter into the equation either.