I am sorry your pet is afflicted with such a disorder. Renal failure is a progressive disorder, even in the face of treatment. The nature of the disorder is that by the time of diagnosis there is already failure of over 75% of the kidney tissue. The rate of decline for each pet is different. The aim of treatment is to alleviate some of the work the kidneys have to perform. It is impossible to predict how long your pet will live. Quality of life is typically good under treatment initially. Over time there will be a decline, but the rate is impossible to determine.