Just to confirm what Deb has said - I emailed that site mentioned earlier, and they say 2 - 3 years.
Begs a question though - how would les flics test them anyway?? Would be amusing to see a gendarm knocking back half a bottle of pastis at the side of the road just to see if a test kit worked!!
FYI - that site is currently out of stock, but are expecting new supplies from Sarkozy Enterprises their suppliers in a few days.
Del