But what's the cost of cooling those bottles when they replace something that was removed? I like the idea of thermal mass in a refrigerator or freezer (it too

But what's the cost of cooling those bottles when they replace something that was removed? I like the idea of thermal mass in a refrigerator or freezer (it took me a while to figure out why milk at home would never last to it's shelf date--the grocery store has a huge thermal mass to it's dairy cases, the milk on the shelf gets much less exposure to warm air than the milk at home) but if you're going to eliminate dead air space I think it's best done with empty boxes, not water.