Never use dry yeast again, because it's so easy to make fresh yeast last forever. Fresh yeast is an essential ingredient in many recipes, especially when baking bread and pastries.
It only lasts for about a week in the fridge and loses steam after a few months in the freezer. Mixing fresh yeast with flour can extend its shelf life. To effectively preserve the yeast, it is best to mix it with flour in a ratio of 1:10. This means that for every unit of fresh yeast there are ten units of flour.