Answers. Best Answer: Store in the Freezer 3 to 6 Months •Store fresh clams in the freezer to keep them fresh the longest. According to the Food and Drug Administration, you can keep fresh shellfish in the freezer for up to six months. After this, it may begin to grow harmful bacteria and should be thrown out.ow long can clams last in the freezer? i got some RAZOR clams 6 months ago and froze them in water. are they still good to eat? i was planning on making clam chowder.