I keep my seeds stock current. There is no guarantee on the seed germination because seed germination doesn't depend on seeds quality only. they require user experience, perfect temperature, proper watering. so i am selling my seeds as is with no guarantee. 
15 Winged Bean Seeds/ Asparagus Bean/ Dragon Bean US seller

Seeds can be difficult to germinate. For better germination, pre-sprout seeds indoors by soaking in water for 24 hours until swollen and then keep at 77°F until sprouted. Scarify seed coats of the ones that did not swell, and resoak. Plant when they sprout. Keep soil moist. Fertilize sparingly. Train to grow on vertical supports. Large vigorous vines can reach 9-12'.

The growing temperature can affect what the plant yields. Lower temperatures increase tuber production; higher temperatures increase leaf and bean production. Fertilizers are not usually needed where fertile soil is present. Keep the area weed-free.