When something starts pecking its way out of the shell, the egg is probably past its prime. Yogurt is spoiled when it starts to look like cottage cheese.
Cottage cheese is spoiled when it starts to look like regular cheese.
Regular cheese is nothing but spoiled milk anyway and can't get any more spoiled than it is already. If it makes you violently ill after you eat it, the mayonnaise is spoiled. This is NOT a marketing ploy to encourage you to throw away perfectly good food so that you'll spend more on groceries. Perhaps you'd benefit by having a calendar in your kitchen. If opening the refrigerator door causes stray animals from a three-block radius to congregate outside your house, the meat is spoiled.