My oldest Heeler is fifteen and a half and has been on steroid tablets (prednisolone) for about 18 months now.
They do make her want to eat all the time and although drinking a lot is a sign of kidney damage, the steroids also make her drink loads. She is happy enough in herself and goes for a walk with the others, although she just potters about behind us. I put a quilted coat on her in the cold weather as she does not run around like the young 'uns. She too has a gurgley tummy sometimes and also coughs quite violently on occasions. It is a case of one day at a time, and when her quality of life becomes too poor I shall let her go with dignity - better a day too soon than a minute too late. I am sure you will know when the time has come to say goodbye, until then make the most of every day, and give her a cuddle from me.