for now.. freeze it! it lasts 5 years or longer in the freezer. I have yeast from costco in my freezer since 1998 and it is still good. the rule of thumb for storing it in the freezer is 5 years.
Another way to store yeast is to make if from flour, water, honey or sugar. to sour it like sourdough then add rye flour. Now if you leave it out on the counter, it will need to be fed everyday in the heat of the summer and less as the weather cools. If you are baking bread every day then you won't need to dump half of it out .. adding more flour, water and sugar to feed it again, stir. the problem with leaving it out on the counter is the flavor will change over time. there is wild yeast in the air and in time it will take over the yeast in the container. the container needs to be glass and a loose top put on. I like using crocks with lids or canning jars with a piece of fabric on top then a ring put on. It must let the carbon dioxide escape.
You can take the above and with a lid that can be put on tightly, put it in the refrigerator. Because it is cold it will inhibit the growth of the yeast and it will only need to be feed once a month. take the jar out of the refrigerator and place on counter. When it gets to room temp. remove half, feed, stir, then put it back into the refrigerator.
You can keep several different types of bread yeast in the refrigerator without worrying about one yeast taking over another.
Before refrigeration, a yeast mixture was formed into a ball and kept in the flour bin. When needed, it was taken out of the bin, a piece pinched off, placed in warm (not hot) water, sugar and given time for it to 'proof'. The ball was put back in the flour bin.
You can take yeast from your refrigerator or counter top, smear it on a piece of fabric, wax paper or paper and let dry. Kept in a cool dark place or share with another. Proof with warm water and sugar.
the above two techniques will live 6 months.
Proofing is checking to see if the yeast is still alive. Place yeast in warm water... again NOT hot ..hot kills the yeast, a little honey or sugar. If it bubbles or froths.. it is alive. If nothing happens it is dead and you need new yeast.
The water should be pure and not tap. Tap water contains chlorine. I use distilled water.
*if you are baking bread and making cheese, wait 1 week (or longer) the cheese yeast will take over the bread yeast and make it taste strange, awful even. this is where having 2 kitchens is nice.