
Of course they are worthless, just send them to me!!!
JUST KIDDING!!!
Seriously, FWIW, I know the official line from Gee Enn See is, "we have to get rid of things by their expiration date, however beyond that we believe the products should deliver 90% potency for at least six months." They won't sell you expired stuff, but if you have a friend that works there, ask for the "expired" products, because 99% of the time the store is supposed to throw them out.
I've used things up to about two years after the date, with apparent fine results.