Crying Over Sour Milk?

The droll, deadpan comic Stephen Wright asked the perplexing question:  how do you know when sour cream goes bad?  It’s a question I’d spent little time and psychic energy on ... until I perused the label of my Kirkland Mature Multi Vitamins and Minerals jar.  It asserts:  freshness and potency guaranteed.  That’s a claim I used to be able to make about myself, but about a vitamins?  How can you know when your tablets are over the hill, have seen better days, or are just too pooped to pop?  Have your supplements lost it when you’re:  no longer faster than a speeding bullet; less powerful than a locomotive; able to leap tall buildings in two bounds?  And, assuming you can tell that your vitamins and mineral tablets have run their course:  freshness and potency guaranteed?  I wonder how many jars of vitamin supplements get returned to Kirkland with sour letters from consumers fuming about flaccid freshness and limp potency ... with a demand for a refund.  In other words, how can one know when a “Mature” product is too mature to do any good?  The expiration date, you say?  Okay, “09/13.”  Does that mean that on September 30 of 2013 I'm good to go, but on October 1, 2013, my vitamins give up the ghost, are less than useless, aren’t worth the plastic they came in?  A recent Budweiser ad campaign touted the “born on date” that’s printed on its beer bottles, implying assured freshness.  But the commercials never explained what the date – “1JAN12,” for example – means.  For how long after January 1 is the beer good?  A week, a month, a year?  I had to go to Budweiser’s website for the answer:  110 days.  So the beer “born” on January 1 is good through April 19.  Does it go skunky on April 20?  And what about the date on a milk container?  Do I need to open the container by that date or finish it by that date?  Oy!