The last few batches of yeasted dough I mixed made OK but not great bread. I thought that the initial proof was a bit weak.
So I decided to test the yeast I've been using.
I buy a 1# (454 g) bag of fas-instant yeast from either Costco or Amazon. I prefer Costco, as it's less expensive, but they don't always carry it.
I put part of the yeast into a snap top plastic container, and then vacu seal the rest and freeze it.
I used the test method from red star yeast. https://redstaryeast.com/yeast-baking-lessons/yeast-shelf-life-storage/yeast-freshness-test/
The test using the in the snap-top-box yeast was not bad, but about 10 - 15% less of a rise in the measuring cup than the protocol said should be the result.
I then tested the yeast I had saved, sealed and frozen. That exceeded the test protocol by about 10 - 15%.
So the yeast had definitely degraded sitting in a cabinet.
Tossed the in-the-cabinet yeast and replaced it with that I had stored.