How long do sunflower seeds last?
Unopened, they keep in the pantry for about 12 months. Once opened, they keep in the pantry for about 3 months.
Product: Shelled sunflower seeds.

Shelf life of sunflower seeds at a glance
| Storage | Unopened | Opened |
|---|---|---|
| Pantry | 12 months | 3 months |
| Fridge | – | 7 months |
Their high oil content makes opened seeds go rancid; airtight, cool storage makes them last longer. A bitter or rancid taste means throw them out.
Do sunflower seeds go bad?
Food past its date has not necessarily gone bad. The times on this page are guideline values for food stored properly. In the US, date labels are not required by federal law (infant formula is the exception), and most of them describe quality, not safety. A "Best if Used By" date is not an expiration date, and many products are still fine after it. A "Sell By" date is meant for the store, not for you. Look at the food and smell it before you taste a little. Mold, an off smell or a bulging can or lid means it goes in the trash. Take a "Use By" date on perishables such as meat, fish, deli meats and dairy seriously: eat or freeze them by that date.