The shelf life of your food storage is affected by many things, perhaps most important are temperature, moisture, atmosphere, and containment.
Here’s more detail…
Temperature
Temperature greatly affects food storage life.
USDA guidelines say each 10°F drop in temperature doubles the storage life (relatively). Similarly each 10°F rise will halve the food storage shelf life.
Having said that, read this regarding use-by and sell-by dates.
An example of the general relationship of food storage shelf life with temperature:
Generally, food shelf life is referenced to room temperature – which we’ll say is 70°F.
80°F (0.5 the stated shelf life)
90°F (0.25 the stated shelf life)
100°F (0.125 the stated shelf life)
OR
60°F (2.0 the stated shelf life)
50°F (4.0 the stated shelf life)
We learn from this how important it is to store your long-term food supplies in the coolest place possible; as in a basement, etc..
Moisture Content
For long term storage, drier is better. The drier the food and the drier the environment, the longer the shelf life – to a point…
For example, grains should maintain a moisture content of 10% or less. Commercially dried foods easily achieve these levels.
Be aware of the likelihood that typical home dehydrated foods might not result in the same moisture levels as from commercially dried foods, and therefore may not last as long. As a rule of thumb, dried foods with 10% or less moisture will snap easily and are very brittle.
Unless the food is packaged in air-tight containment, then the moisture from the environment will work it’s way in over time and reduce it’s shelf life.
Atmosphere
Earth’s atmosphere contains about 78% nitrogen and 21% oxygen. Oxygen oxidizes many of the compounds in food and reduces it’s shelf life over time.
Bacteria, one of several agents which make food go rancid also needs oxygen to grow.
For maximum shelf life, foods should be stored in an oxygen free environment.
Oxygen absorbers dropped into a sealed container or a Mylar bag is common practice for long-term food storage. When the oxygen within the sealed container is absorbed, what remains is 99% pure nitrogen in a partial vacuum – a good atmospheric condition for food storage.
Note that it is important that the container you are using must be able to hold an air-tight seal over time.
Container
To get the best storage life for most food products, the product container must have a hermetic (air tight) seal, and ideally be opaque or stored away from sunlight. Common methods used include vacuum sealed bags, sealed cans or jars, sealed food storage buckets, and sealed Mylar bags.
If using 5-gallon plastic buckets, be sure that they are rated ‘food grade’. Remember that just because a bucket is HDPE #2 does not necessarily mean that it is food grade.
Safe Plastics for Food and Drink
4 Things That Affect Food Storage
Modern Survival Blog