Our Gracie, who was 3/4 Great Dane, amazingly lived to be 14 1/2, which her vet attributed to her being spoiled rotten. I can attest to the fact that they will eat you out of house and home while growing up (at least 18 months) but after that, don't eat more than any other big dog. Gracie got 4-5 cups of kibble with whatever add-ibns were available that day from the people cooking, of a 1/4 can of wet dog food mixed in, just once a day as an adult, slightly less when she was a senior and slowing down. Gracie was around 145 pounds at her optimal weight.