I am sorry for the diagnosis. Yes I have dealt with a pet with kidney failure. She was also put on special food, but she was already having problems digesting by the time we figured there was an issue and almost 15YO. She was very picky with food (loss of appetite) and I was cooking for her low protein bisquits (with renal supplements from the vet) the last few months.
The vet told us it is all dependant on the dog and progression of disease, but she has seen some pets live for up to a year on the special diet. Also as mentioned above, kidney function can improve. My girl also had an infection and infection can give higher kidney enzymes. If I could give you any advice, try your best to keep her happy and that just means being patient and doing all you can for her. I tried hard not to dwell on the fact that she was ill and she honestly was a super happy girl until she couldn't anymore.