Great question! I looked it up and found this simple list. This should help you and everyone else out. Vegetable seed viability
beans - 3 years beets - 2 years carrots - 3 years corn - 2 years cucumbers - 5 years lettuce - 3 years peas - 3 years peppers - 2 years pumpkins - 4 years radishes - 5 years spinach - 5 years tomato - 4 years watermelon - 4 years