I would speak to your vet, I am not sure if Liquivite contains the right balance of taurine etc to be fed as an only food for that length of time. A/D is a brilliant food, very few cats turn it down (tom did when his teeth bothered him, then wolfed it after they were done, but think he is hte only one to turn it down), and if I had to feed one of those for that time, it would be A/d - again, can only be bought from vets or VetUK (but you have to bulk buy from VetUK), around £1.10 a tin.