I have some heirloom butterbean seeds that I grow every year. I have about a half gallon of these seeds stored in "air-tight" containers underneath my bar. The bar is closed-off and the sun cannot shine on these seeds and my house if cooler than most houses with temps in the low 60's in winter and mid 70's in the summer. My questions: How long will these seeds be viable? Can I improve this time by doing something differently, i.e. freezing or refridgerating? Thanks for the responses.