What’s the difference between the three-month and longer-term supply items?

Answer:

Three-month supply items are foods that you normally eat, including canned and commercially packaged foods. Longer-term supply items are basic food items like grains and beans that have very low moisture content (about 10% or less), can be stored for long periods of time (20–30 years), and would sustain life if nothing else were available to eat. A portion of longer-term supply items may be rotated into the three-month supply.