Some vegetable seeds retain their viability longer than others do. They can be divided into 3 general groups: (1) comparatively short-lived, and usually not good after 1 year; (2) moderately long-lived, often good for 2 to 3 year; and (3) long-lived, often retaining good viability for more than 3 years. Listed below are some of the more commonly grown vegetables and the average length of time the seeds can be stored with resultant satisfactory germination. Dry, cool storage is presumed. 

Average Length of Time to Store Seeds in Years

Beans 3
Beets 4
Brussels sprouts 3
Cabbage 3
Carrot 3
Cauliflower 3
Corn 2
Cucumber 4
Eggplant 4
Leeks 2
Lettuce 3
Muskmelon 4
Okra 2
Onion 1
Parsley 1
Parsnip 1
Peas 3
Pepper 3
Pumpkin 4
Radish 3
Spinach 3
Squash 4
Tomato 4
Turnip 3
Watermelon 3