I always store mine in a tightly sealed jar in the fridge. Even when I buy a ton and it sits for months and months, I've never had it fail.

Wish I had a substitute handy but work is killing me today and my brain isn't working...

It was commercial yeast sold in bulk at a health food store. It came in pellets instead of powder, and I think that had something to do with its remarkable longevity.

I know the only time I proof yeast in warm water and barley malt is when I know it's old yeast and I want to make sure it's still alive. Otherwise, I don't proof it before baking, I've killed it off that way too many times.

I keep the open jar or package in the freezer. I kept the unopened jar in my cool, dark pantry.

I'd start the yeast on its own for years, then learned I was proofing it Never too old to learn.

I am trying to make a sourdough starter, and it doesn't look promising. I'll try to exchange this jar.

The last jar of yeast I bought had it stamped on the label. There might also be a lot or batch humber on it, you don't want a replacement jar from the same lot or batch, it would be dud yeast, also.

Hope the next one works out better. There's little worse for a bread baker than expecting bread and getting a brick.

I wrote the company and they sent me coupons for two free jars!

Glad you had a good result

Nothing better than fresh baked bread. I, too would try to return the jar. Very frustrating to do all the work for a poor result!

So I buy individual packets.
Then proof them before adding flour.

The slow rise could give you a more complex flavor.
Good luck.

I tried starting some sour dough, and even after 24 hours, no luck. I'll try to exchange it.

I always used the small packets, but one year, my daughter got me a large package of bulk yeast and I've been a fan every since. I kept it in the freezer and it lasted way past its expiration date.