Do you mean that you use it for making the chili or that you drink it primarily with chili? When you're cooking with beer, you can use beer that is less drinkable, so if a beer is amazing, you should use it for drinking, IMO.
If they are bottled in our standard Mr. Beer PET bottles, they have about a year shelf life. If they are in our oxygen barrier PET bottles, they can last for up to 3 years or so. If they are in glass, they will last indefinitely. But most beers peak in flavor after 6 months to a year. After that, they don't improve much (the exceptions would be a barrel aged barleywine, porter, stout, or biere de garde style).