Ya, I had a wyeast smack pack that was a year past the best before date....gave it a smack..nothing for 4 days, the it took off. I have used this yeast for 3 beers (recultured) this year.
As HB 99 said, give it at 4-5 days before giving up on it. I was about to throw it out - but then saw it sewlled a bit after 4 days ...then balloned after another 12 hrs.
Primary : 5.5 G of Hard Cider
On Order: Got it all..for a few months
Thinking about: Plisner malt and saaz hops
Drinking: 5 G- Kidney_Punch Wine, 10 G Canadian Pils, Euro Pilz