My wife and I keep a stick of butter in the cupboard rather than the refrigerator. Even with just the two of us, it rarely lasts very long, but I'd say it may go as long as a week without refrigeration before it's all gone. There have been times when I have told friends about this and they express concern due to the fact that butter is a dairy product. They cannot comprehend not refrigerating it at all times.
What allows butter to stay perfectly tasty and edible, even after a week outside of the refrigerator, where milk, sour cream, or cheese would be foul in a day or less?