I did some research on the storage life of yeast. I started with this article: Red Star Yeast which sates:
"Each package and jar of dry yeast is stamped with a 'Best if Used by' date. This date is two years from the date the yeast was packaged. The month and year reflect when you should use your yeast by. The last 4 digits are for manufacturing purposes and have nothing to do with when to use the yeast by.
"Example of code: FEB 2010 08 09 - Use by February 2010
"Unopened packages and jars should be stored in a cool, dry place such as a cupboard; and can also be stored in the refrigerator or freezer. Yeast 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 (see storage tips below). Under these conditions, we recommend using the Dry Yeast within 4 months after opening if refrigerated, or within 6 months after opening if frozen.
"Dry Yeast should be at room temperature before using . When you are ready to bake, take out only the amount of yeast needed for your recipe and let it sit at room temperature for 30-45 minutes before using. Immediately put remaining yeast back into storage, following the storage tips below.
Yeast is a living organism, and will lose activity over time - even if the package is unopened. If you are unsure of your yeast's activity, perform the Yeast Freshness Test before using."
"We offer SAF yeast in vacuum sealed 1 lb. packages. The yeast is granulated and until the package is opened it feels almost like a solid brick because of the airtight vacuum seal. The packages are printed with the date of production as well as a "best if used by" date. The "best if used by" date is set 1 year from the date of production, and in doing this, SAF assumes that you open the package as soon as you get it and keep the entire opened package at room temperature. Instead, we recommend that you open the original container and pour a portion of it into a small resealable container to keep in your cupboard (not out in the light) for daily use (a baby food jar works fine.) Then roll the top of the SAF container down, clip it so it doesn't unroll, and store it in your freezer. Kept this way, the yeast in the cupboard will be good for a least 1 year and the remaining yeast in the freezer will remain good for a minimum of 5 years. We know from experience that SAF yeast, stored frozen in a re-closed container, retains its potency for several years. If you have a small airtight container for the frozen yeast, that can be used in place of rolling and clipping the foil pouch. When you transfer more yeast to your cupboard container, that yeast will remain good for another year in the cupboard. Unopened, vacuum-sealed containers of SAF yeast stored in the freezer actually remain potent for 10 years or more."
More On SAF Yeast:
This article says frozen shelf life is 10-15 years and one pound of yeast makes 96 loaves of bread. One of the comments says it works using it straight from the freezer, it doesn't have to be brought up to room temperature.
This article says this yeast reduces the amount of yeast needed in a recipe by 25% and that it is GMO free. That means a one-pound package will make more than 96 loaves.
SAF Instant Dry Yeast for Baking
King Arthur Flour's yeast article-- Excellent article!
More on the differences between Instant and Active yeast. Are Active and Dry yeast interchangeable? Difference between SAF red label and SAF gold label yeast. "A vacuum-sealed bag of yeast stored at room temperature will remain fresh indefinitely. Once the seal is broken, it should go into the freezer for optimum shelf life." Use glass or acrylic air-tight containers to store in freezer. Also concurs that you need not defrost yeast and can use it straight from the freezer. If you double your bread recipe, do you double the yeast?
And FAQs from the manufacturer.
The Difference Between Instant Yeast & Active Yeast
"Both active dry yeast and instant yeast are designed to be used in recipes for breads and other yeast doughs. Instant dry yeast has the additional function of multiplying quickly, causing dough to rise in a shorter time.
"Both types of yeast are sold in individual packets and in larger jars by many different companies. Instant dry yeast is also sold under the names of bread machine yeast and Fleischmann's RapidRise yeast.
"When mixing dough, active dry yeast should be combined with warm water before being added to other ingredients. Instant dry yeast, on the other hand, should be mixed directly into dry ingredients, and then the liquids should be heated to 120 degrees F and added.
"Active dry yeast requires about two hours to cause the dough to double in size. Instant dry yeast only takes ten minutes to multiply enough for the dough to double in size.
"Bread made with instant dry yeast may not have as good of a flavor as bread made with active dry yeast. To improve the flavor, allow bread to rise more slowly in the refrigerator overnight.
Conversion factors amongst types of yeast at the Wild Yeast blog
Regards, - Cheryl N.