We also freeze anything that isn't in a can or a sealed, so bread we usually buy 4 loaves and freeze 2 or 3, and accept we'll have to get more from the store before we go.
The limitation is we can't get things from Costco that aren't used regularly, for example, we don't go through enough cream cheese to buy Costco size, and it doesn't account for all our food needs. But if tomorrow I lost my job we know we could survive without having to go to the store for anything but milk and eggs* for the next month or two.
* Hopefully we'll remedy this in the summer with chickens.
I've been contemplating somehow tracking the pounds of food bought per trip as a quick informer on the spot. The tricky thing is that the kids are growing so their consumption has a steady ramp but not yet enough for a timely consumption of stuff like cream cheese etc. Lots of products seem to be in the 2lb range. 2lb is actually a good deal of food I'm finding out.