I store my dry yeast in the freezer with no problem. It does keep much longer pass the expiration date. You will want to let it warm up to room temperature before use so you don’t shock them to death adding to warm wort. The reason you can’t freezer liquid yeast is that because of the ice when it forms it’s sharp and punture’s the yeast cell killing it
From Danstar FAQs:
"Should I refrigerate or freeze my dry yeast until I use it?
Yes, although dry yeast can be stored at room temperature and performs well for the duration of the shelf life it is preferable to store it at colder temperatures. Dry yeast will always lose some of its viability and activity over time but at colder temperatures these losses are less than at warmer temperatures. If you choose to freeze your dry yeast for storage, let it warm to room temperature in the package before rehydration & pitching."
