WYEAST 1056, how long can it be stored and still be good?

I brewed a pale ale yesterday and pitched a WYEAST 1056 American Ale smack pack that I had sitting in the fridge since last year. I had been brewing lagers almost exclusively but decided to brew me a good pale ale last year and bought the pack, but never got around to it. I finally decided to brew an ale on a whim yesterday and used the yeast. I did not make a starter and pitched directly from the sanitized pack. Nearly 24 hours later and still there is no visible signs of fermentation. I added some yeast energizer to it yesterday too just in case, but that didn't seem to work. I have not taken another SG reading but I'd assume it will be the same as my OG.

Anyone have any experience using old smack packs? The manafacture date on the pack was March of 2009. Is that too old to pitch? It's no big deal. I could run up to my LHBS today and grab some more yeast but I was just wondering if anyone else had any problems with slow fermentation with these things after such an extended period of time?

If it sat that long I would have made a starter. Thats really too old to be using right out of the pack and likely resulted in under-pitching.

24 hours is not that long though - I'd wait at least 48 before thinking about pitching more yeast. You just never know with yeast.

Well, normally I would have made a starter but I brewed this baby on a whim. I'm going to the LHBS store today anyway and will just go ahead and pick up a safale 05 just in case.

I agree its too early to tell. I would bet you are not going to see visible signs of fermentation until 3 days after pitching.

Well, I still had not seen any sign if bubbles in the air lock so I popped the bucket lid and checked the wort this afternoon, and low and behold there is a thick layer of kraeusen on the top. So I guess it's fermenting out, there just isn't anything going on in the airlock.