At fifteen she is entitled to be a bit deaf, blind and creaky, but as long as she is eating well, able to get herself out to go to the toilet and has a good quality of life then I wouldn't worry too much, dogs cope quite well particularly if these things have come on over a period of time. If however, any of these things are affecting her you need to seriously think about whether her quality of life is still good enough. She may well go on for another year or two, but unless those years are spent comfortably and in no distress or fear then you have to ask who are you keeping her going for - her or you? Most dogs let you know when they have 'had enough' and if the vet feels she is ok then you just need to make the most of your remaining time with her. I hope you have her for a while yet and you both enjoy your time together. Just remember though, when you have to make the decision its better a day too soon than a moment too late. xxxx