Wood pellets can last indefinitely if kept in the right environment.
The key to preserving your pellet supply is to ensure they are kept dry and at a consistent temperature. Choosing a good, airtight hopper or silo will protect your pellets from exposure to water and pests. Likewise, try to keep your pellets in a temperature-controlled environment that doesn’t get too hot or too cold throughout the year.
This will help ensure that your pellets continue to burn with maximum efficiency and prevent you from losing your pellets to rot.