I usually buy an 8 pound bag of Nutro NC Kitten for my 10 and 11 month olds but they are growing so big (maine coons) and consuming more food. Also they are not eating canned food right now because my girl broke out with sores from one of the canned foods so we are limiting her diet at the moment. They are going through the bag pretty quickly. I was thinking of buying the 20 pound bag since it would save quite a bit of money but I'm wondering how long it will keep once open? Does anyone else buy the really large bags for just 2 cats? They love it when I open a fresh bag. They can clearly tell the difference between it and a bag that has been open 3-4 weeks.