I watched a tv show about Coffee beans and how theyre worked with in factory on 'How Stuff Works' tv show. they said you should treat your coffee beans like you do a loaf of bread, you should buy new coffee beans every week or so.
Believe it or not, and this is off-topic but another funny cool thing I leanred on the tv show. In some places, you can buy coffee beans pooped out of animals! There's a certain species of lemur (i think?) that sniffs out the most potent coffee beans, eats them, and then poops them out. Their digestive tract won't process the coffee bean so collectors will then go and grab the poo beans , clean them off and sell them. They are expensive though and from what I've heard, extremely good and potent coffee blend.
Anyhow, i hope this helps... I buy small bags of coffee beans that i know is a week's worth, then i just buy another.
Also, if anyone has any recommendations for coffees, im in dire needs of trying new coffee blends. Please pm me if you have some, thanks guys.