Let's say 1 gallon per week that would take 1/2 pound of soybeans.Or you could say; 9 ounces of soybeans per gallon. (252 grams per 1 gallon of milk)
They should keep for one year after production date. Of course, they will keep longer if refrigerated.
Over a year of kept in a relatively cool dry place in a sealed container.
Keep them in a relatively cool dry place. Refrigeration is not necessary. Keep them in a sealed container. Their main enemies are moisture and insects.