I don't know how other "big" families do it, but on average we grocery shop at least one or two big trips a month and then little smaller trips in between. Most of our big trips are to stock up on things we use alot. The smaller ones are for little forgotten things or milk, bread, etc.
When we first moved into this house, our kitchen while bigger than the last house, didn't really have a lot of cupboards. So, I asked Rich to turn the coat closet (right off the kitchen) into a pantry. We eventually out grew that as well, so we turned a small downstairs room into a pantry/storage room. And this is how it's been for the last few years now. I'm happy with the room, it has lots of shelves to store food and rubbermaid storage boxes that hold the kids' toys.
Just thought it would be fun to share pics of my little "store".