How long can I hold open dry yeast???

I bought a pack of us-05 to add some yeast to a batch and I only used a little bit. So now I've got like 3/4 of a pack in the fridge and it's been there for 10 days or so. Fermentis website says 7 days below 39 degrees, do you think I'm safe to use it for a small batch of cider? Will adding a nutrient help? Oh, it is in a ziplock bag in the fridge.

It should be ok. I split packs sometimes on big batches, I seal the end up with my food saver. Never a problem yet.

A few years ago, when I was first playing aorund with wine, I used half a pack of some generic dry wine yeast for a batch and left the other half open and sitting in the back of a shelf in the bathroom for 2 years. I found it, and was curious about whether it was still good, so I cooked up a simple table sugar, water, and yeast nutrient solution and tossed it in there; it was still good. Could have been an infection, of course. However, YMMV, of course.

I'd toss it. It's cheap and several friends have had bad luck reusing opened yeast packs. To me, it's not worth risking a batch for a couple bucks.

There ya go...just pick the answer you wanted to hear....

1. use it
2. maybe??
3. toss it...n/g

Well I guess fate made the decision. I was actually going to grab it to take out of town to a friends house to get him interested in brewing. So I packed everything except the yeast. So I stopped by a brew store down south and got a fresh pack and started a batch of cider.