This quote from a Wyeast representative was posted on another home brewing site:
Wyeast recently switched over to a Best if Used By date, which still guarantees our products for at least 6 months from when they are manufactured. When stored and handled correctly (never allowing the yeast to come above refrigeration temperature until ready to activate), the viability and health of the yeast is very stable. We still recommend making a starter when the yeast is within 2 months of the BB date to ensure you are pitching a robust culture.
We are familiar with the homebrew calculators that factor in the manufacturing dates, but these do not correctly reflect the quality of our yeast. Because many if not all are based on other suppliers? information, and were not consulted or developed with Wyeast, I would like to offer the assurance that our yeast products will perform reliably following our product instructions and guarantee. When viability is incorrectly factored in and a larger than needed started is made, you can end up with too much yeast growth, too rapid of a fermentation, and negative influences on your beer.
The statement that I made
bold would suggest that there is NOT 100 billion cells remaining within 2 months of the best used date. So, WTH. Guess I'll subtract 2 months from the best buy date, and presume either 100 billion cells at that point, or subtract 6 months from that point to assume mfg date???
