I bought a vial of WLP001 Cal Ale yeast last fall and have kept it in the dark fridge ever since. I think it's "best before date" is Jan 02, 2014, making the production date Sept 02, 2013. I am making an Imperial Stout this weekend that calls for that strain but am debating as to whether or not to use the vial I have or get a fresh one. I made a 1.6L starter (4oz of DME) and have it on the stir plate. There is definitely yeast activity and I was thinking to step it up by decanting and doing another 1.6L starter. When I plug in the strain and age, Beersmith tells me I'm at like 29.6Billion cells without starter, and 177.2Billion cells with my 1.6L starter on stir plate, if I step it up with one more 1.6L dose of wort I should be right around the cell count for pitching called for by beersmith (313 Billion). However if I check the brewersfriend calculator it tells me that vial has 0% viability! Any ideas?