My cat is around 4 years old. I used to give her and her sister each 1.375 oz of food. Now that I have only one cat, I've been giving her 2.75 oz of food. I think this is too much and I want to cut her back to 1.83oz. The problem is that this sections up cat food into thirds and I think the cat food is only good in the refrigerator for two days. How long is cat food good for in the refrigerator? How much is enough for a single serving from a 5.5 oz can?