Check the batch code on the upper-left corner of the instructions sheet thats with the QF. The batch code means the date of manufacture, in which the 2 year shelf life begins.
Example: If the QF batch was manufactured in June 2006, the batch code would be F-6B06. Meaning the second week of June '06.

You can always test the QF if you have any doubts about its reliability. Order some Urinecheck 7 adulteration test sticks which can be found by doing a Google search.