I have heard that storing nail polish in the refrigerator will prolong the shelf life. Is this true?

No. It is not recommended to store polish in the refrigerator because it can cause it to thicken. Once taken out of the cold, it could take quite awhile to warm up to room temperature. Today's polish formulas and preservatives improve the shelf life of polish. To thin polish that has thickened, add a couple drops of nail polish thinner.