Baked eggshells do have a long shelf life, but it's important to store them properly to prevent them from going rancid or stale.
To store baked eggshells, make sure they are completely cooled and dried before placing them in an airtight container. You can keep the container in a cool, dry place such as a pantry or cupboard.
Baked eggshells can provide a great source of calcium for your chickens, but it's important to monitor their calcium intake and adjust the amount of eggshells you provide accordingly. Excessive calcium intake can lead to kidney problems or other health issues in chickens.
As for the recommended time to use baked eggshells, it's generally best to use them within a few months to ensure freshness and quality. However, if properly stored, they can be used for up to a year. Make sure to check for any signs of spoilage, such as a rancid odor or discoloration, before feeding them to your chickens.