Storing Dry Yeast

How long can I store an opened package of dry yeast before I have to use it.

I'm planning on brewing 2.5 gallon batches and using Safale Yeast. Mr. Malty gives the pitch rate as about 5 grams for under 1.050 gravity. The packs are 11.5 grams, and I store them in the refrigerator.

Fermentis recommends using an opened pack within 7 days, but I was wondering if anyone had success with longer storage times.

I would toss it if I weren't planning on using it in 7 days...dry is cheap...why risk it?

I'd toss it as well. But several LHBS's repackage some of the Fermentis dry yeasts from bulk into small packets and those seem to do alright. Vacuum sealing in a clean environment is important for long term viability.

I just looked at a package of S-05 I have in the fridge. I states that it should be stored in an airtight container after opening, and be used within 7 days.

I have used half a pack for 2.5 gallon batches several times. I fold the package over, tape it shut and stick it back in the fridge. I have stored them for months and have never had a problem... always vigorous fermentation visible within 12-24 hours.

Just thought I'd share my experience.. I've had an open packet of Danstar Nottingham Ale yeast stored in a ziplock bag in my fridge for about a month now, just used the last of it yesterday and fermentation took off great.

Sanitize the packet before opening and handle with clean hands, refrigerate in a clean airtight ziplock bag with as much air pressed out as possible. That is what I do and one month later it seems to be working just as well as when I opened it.

vacuum sealed yeast can be stored in the freezer. Oxygen is the killer.