Fresh compressed yeast should be wrapped and kept in the refrigerator, it may be frozen however does lose a little bounce. When the yeast truns very brown, green or moldy it has lost it's usable life. Fresh yeast lasts only a week or so. (+ or -) Active dry and instant can be kept in an airtight container in the frig or on a shelf if used within a few weeks in a cool dry place. If you are in a warm moist area, best to keep yeast in the cooler. happy proofing!