Every get a beer that just tastes old? I have. And it always makes me look for a born on date or a best buy date and then I kick myself for not looking before I bought it.
Well to help remedy this situation, there is a website called BeerDates.com.
Now they only have a minor amount of California breweries but you can use that to extrapolate out and make a better guess on some of the more esoteric labels to get a better freshness handle.
Some breweries like Eagle Rock and Sierra Nevada have added better/clearer information but more need to do so.