I never throw anything out,unless it thawed.I have some like year old shrimp on skewer that are all frosted up.
I thaw and pull them off the skewer,chop and feed.
I've used some pretty old food. Just make sure you thaw it and wash it all off in RODI. I take my cubes and put them in a brine net, then slowly pour RODI over it until its all thawed and washed off...