As again, it is rather subjective. My recommendation is to
forget about it and stick to the safety measures imprinted by the
manufacturers. But as I have no knowledge of the tricks of the
trades in the food packing company in terms of setting an expiry
date, I shall leave this discussion to alexkusu who will give you a
better idea and picture of what is happening.
After all, in wartimes, soldiers fighting for long periods of time
don't get good food to eat, but surprisingly they still survive. It
all depends variably in one's immune system. Some people sort of
being said to have a stronger gut resistance while others have
weaker resistance (hence manifesting as diarrhea, constipation,
abdominal pain, bloatedness and excessive wind).
Since it is rather subjective, I shall remain quiescent 
