I'm finally bringing my little guy home the 29th of April and I can't wait! Riley will be about 11 weeks at the time. I was wondering about how long a 20lb bag of food lasts a pup his age. One of the great perks of vet school is that I get Hill's food cheap, but the store is only open during the school year, so I'll have to stock up for the summer. Will 40lbs do it, or do I need closer to 60 to last me through August? Thanks guys!