Plants that are not under USDA inspection are governed by the laws of their states. Recently Pepsi started what I suspect will be a major trend - advertising and branding freshness. This is because its artificial sweetener, Nutrasweet, loses its flavor over time. If you store Diet Pepsi in a warm area, it will lose sweetness faster. The amount of time you should allow before consuming the product depends on what it is, and how it's packaged.
Temperature is key Temperature remains one of the most critical ways to maintain freshness.
Manufacturers and retailers must ensure that product temperatures in shipping and storage are at proper levels. If you see ice cream that's soft in the freezer case, or milk that's not cold - don't buy it. The same rule pertains to all fresh products.