When you buy milk, salad greens or yogurt in the supermarket, you always look at the expiration date. Our medications, too, contain expiration dates, as the strength of the dosage decreases over time. Even retail store receipts include a date by which items must be returned.
However, when a young woman signs a prenuptial agreement, she does not believe it will ever be needed and waives her alimony claim prior to her marriage.