Most commercially available dry beer yeast has an expiration date of between 1-3 years while liquid yeasts have a printed date of between 3-6 months but both can sometimes be used past this date.
Canned yeast starters do not need to be refrigerated and have a shelf life of about a year.
Unlike most perishable food, yeast won’t necessarily “go bad” in the sense that it will spoil, rot, or become dangerous to consume. Typically, commercially available beer yeast will come with a recommended use-by, best-by, or expiration date.
Yes, just about any beer yeast that you buy at a homebrew store or from an online homebrew supply will have some sort of expiration date printed on it.
The date on beer yeast may be expressed as a “best by” date. Regardless of whether the date on your yeast is listed as an expiration or a best by date, you should try to use the yeast before that date.
The good news is, no matter what the expiration date on the package says, if you’re able to confirm yeast activity you can go ahead and use it in your next batch of homebrew. It’s perfectly safe to use.
If you don’t see foam or bubbles after an hour, your yeast is likely dead and not salvageable. In this case, the liquid would look opaque as well as “flat” like tap water
The key to getting the most out of your yeast is making sure to store it properly. Because yeast is a living thing, it needs to be cared for in order to thrive. Different types of yeast require different storage conditions.