Most food products lose nutrients over time. Prepared foods come with a date stamped expiration, after which the manufacturer does not recommend use. Notwithstanding the date stamp, many foods will still be edible long after that date. The reason for following the guidelines, is that knowing which foods fall into the category of extended shelf life is very difficult to predict.
However, there is a whole category of foods that have tested to extra long shelf life. As quoted from the Provident Living Website, "While there is a decline in nutritional quality and taste over time, depending on the original quality of food and how it was processed, packaged, and stored, the studies show that even after being stored long-term, the food will help sustain life in an emergency."
Those foods that store well for as long as 30 years, so long as they are kept dry and free from pest infestation, are wheat, white rice, corn, sugar, pinto beans, rolled oats, pasta, potato flakes and apple slices. Both non-fat powdered milk and dehydrated carrots can last as long as 20 years. Some other staples that have a long shelf life include items like salt, baking soda, and Vitamin C.
Foods high in oil and vegetable oil itself may only last one or two years.
Short term storage works well with a system of rotation, putting the newly purchased items in the back in a first in-first out system of management. If you inventory your food supply and find items that are older and have not been consumed, you can draw the conclusion that your particular needs do not include that item.
In all food storage situations, local laws and ordinances concerning food should be observed. Although in the U.S. food storage is somewhat unusual, it is not bizarre or strange to have a adequate food supply for times of need or emergency.