Many of us have had failures when making bread and it does not rise. This is normally because we are using old yeast. According to the manufacturers, it normally stores for about two years at room temperature and three to five in the freezer. Depending on your storage conditions and the packaging, there are exceptions to this.
Yeast stores best when kept cold or frozen in its original sealed packaging. It is very perishable when exposed to air, moisture and/or heat. Once your package or jar is opened, the yeast must be refrigerated or frozen in an airtight container. Make the packaging as small as possible to eliminate as much oxygen as possible.
I recommend that if your yeast is getting on the old side that you proof it prior to use. Fleischmann’s has the following instructions on their website on how to proof yeast.
To proof it, add 1 teaspoon sugar to 1/4 cup warm water (100° to 110° F). Stir in 1 envelope yeast or 2 1/4 teaspoons; let it stand 10 minutes. If the yeast foams to the 1/2 cup mark, it is active and you may use it in your recipe. Just allow for the extra ¼ cup of liquid in your recipe.
If you have waited 15 minutes or so and have not seen any foaming, your yeast is dead. If the yeast still shows some partially foams under normal conditions, go ahead and throw it out.
However, in an emergency, if you see some foaming it still has some life left in it. This gives you the opportunity to increase the amount in your recipe and still get your bread to rise. This will take some guesswork on your part.
You should rotate your yeast on a regular basis so that your stored yeast is as fresh as possible.