This is important, as consumers enjoy fresher goods, and furthermore some stores can be fined for selling out of date products; most if not all would have to mark such products down as wasted, resulting in a financial loss.Shelf life depends on the degradation mechanism of the specific product.The usually quoted rule of thumb is that chemical reactions double their rate for each temperature increase of 10 °C (18 °F) because activation energy barriers are more easily surmounted at higher temperatures.

However, improper storage of milk may result in bacterial contamination or spoilage before the expiration date.

The expiration date of pharmaceuticals specifies the date the manufacturer guarantees the full potency and safety of a drug.

There is a widespread impression, for instance in industry, that "triple time" can be simulated in practice by increasing the temperature by 15 °C (27 °F), e.g., storing a product for one month at 35 °C (95 °F) simulates three months at 20 °C (68 °F).

This is mathematically incorrect (if the rule was precisely accurate the required temperature increase would be about 15.8 °C (28.4 °F)), and in any case the rule is only a rough approximation and cannot always be relied on.

The same is true, up to a point, of the chemical reactions of living things.

They are usually catalyzed by enzymes which change reaction rates, but with no variation in catalytic action, the rule of thumb is still mostly applicable.

However most reactions are accelerated by high temperatures, and the degradation of foods and pharmaceuticals is no exception. liable to be triggered to explode by very small disturbances, even trivial jiggling) than more recently manufactured explosives.

The same applies to the breakdown of many chemical explosives into more unstable compounds. Rubber products also degrade as sulphur bonds induced during vulcanization revert; this is why old rubber bands and other rubber products soften and get crispy, and lose their elasticity as they age.

However, shelf life alone is not an accurate indicator of how long the food can safely be stored.