To maintain your Bivy Sack, ensure it's clean and dry before storage to prevent mold and mildew. Clean it by wiping off dirt and debris with a damp cloth, and avoid using harsh detergents or machine washing, as this can damage the waterproof coating. If your Bivy Sack's waterproofing starts to degrade, consider reapplying a DWR (Durable Water Repellent) treatment to restore its water resistance.