If a lot of your electronics require D batteries, or you want to be prepared for an emergency, buying D batteries in bulk is a good choice.
When do D batteries expire?
Most types of alkaline D batteries have a shelf life of 10 years.
What are D batteries used in?
D batteries are most often used in larger flashlights, but can also be needed by musical equipment, electronic toys, radios, and transmitters. D battery size, voltage and current are standardized to be compatible with a wide variety of home electronic gadgets.