Bean seeds generally last for at least three years if they are stored in a cool, dry location. However, planting seeds haphazardly in hopes they grow is a waste of valuable gardening time. If you aren't sure about the quality of saved bean seeds, germinating a few of the seeds in a clear plastic bag will help you estimate what percentage of the beans are viable and worth planting.
Moisten a paper towel. Squeeze the paper towel so it is damp but not dripping. The beans will rot in too much moisture.
Lay the damp paper towel on a flat surface. Count several beans and place them on the towel, equally spaced. A number such as 10 simplifies the mathematical calculation. Discard beans that are cracked or shriveled; damaged beans will skew the results.
Place another moist paper towel on top of the first towel so the beans are between the two layers.
Roll the paper towel carefully and place it in a resealable plastic bag.
Mark the date on the outside of the bag. Place the bag in a warm location away from direct heat or bright sunlight; bean seeds don't require sunlight to germinate.
Remove the paper towel from the plastic bag after three to five days. Unroll the towel carefully and count the beans with sprouts at least 1 1/2 inch and at least one strong root. Bean seeds with shorter sprouts have a slower germination time and are probably not viable.
Determine the rate of germination. For example, if five of 10 seeds germinate, you can reasonably expect that 50 percent of your saved beans are viable.