Most modern fridges and freezers have an auto defrost cycle they run once a day. If you have the bloodworms in the freezer and it has an auto defrost cycle, try to use them up within 1 month. If you have a chest freezer, they don't normally have an auto defrost cycle and frozen food can last a year or more in that.
If your freezer does have an auto defrost cycle, put the packets of bloodworms and other frozen fish food into an icecream bucket with a block of ice or freezer bottle in the bottom of the bucket and keep the lid on it. Put the bucket in the middle of the freezer away from the back because the back is the hottest part when defrosting.