Earl: First off, thanks so much for the lovely picture!
Second: the number of Stingers left over from the Muj versus Russians days is a number one can sort out via web search and guesswork, perhaps. It is greater than zero. When I was involved in that theater, we worried as much about old stingers, and who might have one, as we did about a variety of Eastern Bloc MANPADS. While the more common threat to helicopters was small arms fire (AAA below 37mm I think is the criterion, it may be AAA below 25mm, memory foggy) the possibility of a MANPAD being still in working condition is again, greater than zero. That realization informs a lot of air operational method.
As to the shelf life answer of a "long time" I'll let that go with "for selected definitions of "long," maybe so. Included in risk assessments regarding Stinger is that they don't just sit on a shelf.
I was amused by the assertion that Stingers of the 80's generation (a heat seeking missile) are somehow able to identify American exhaust, or heat signature from various quarters of American aircraft, and thus not attack. That's a neat rumor to keep alive.
Earl: What is claimed by Talib and various other folk for consumption by the international media is just that, claim, which is often either hard to confirm, can't be confirmed, and even just plain false.
It is also sometimes true ... quite a lottery, which makes your poker player allusion very fitting.
If, since 2001, one helicopter has been brought down by a MANPAD, given the number of helicopter sorties that have been flown in Afghanistan, that puts MANPAD well below the usual threats of crew error, FOD, maintenance trouble, small arms fire, and RPGs.
FWIW.