I had some White Labs vials in the fridge, that was dated for use by March 2012, that I used this past weekend. I made three starter steps to get the cell count where I needed. After pitching the slurry, I had full activity in under 12 hours (going through the blowoff assembly)...
With a starter, or a couple of starter steps, you can use rather old yeast.
Hopping Tango Brewery
跟猴子比丟屎 ・ Gun HOE-tze bee DIO-se
On Tap: Caramel Ale, Mocha Porter II, MO SMaSH IPA
Waiting/Carbonating: 12.5% Wee Honey II, 8.9% Old Ale, English Brown Ale, Lickah ESB, Mocha Porter II
K2: Epic mead
On Deck: Caramel Ale
Mead [bottled]:Oaked Wildflower Traditional, Mocha Madness, Blackberry Melomel, maple wine