The time that things keep in a freezer is a factor of the temperature mainly. Fish keeps about 3 months in a domestic freezer (-10 deg), 6 months in a commercial freezer (-18 deg) and about a year at -30 deg. If it is not sealed properly it will suffer from feezer burn which is a bit like freeze drying. I feed a lot of blood worms and I keep it about a year sometimes. If you freeze a strawberry in liquid nitrogen it freezes instantly and when it thaws it is still pretty good quality because the ice crystals are very small and little damage occurs. If you freeze one slowly in your domestic freezer then thaw it out it turns to mush because it contained large ice crystals that penetrated all the cell walls and damaged it. Thawing on the way home and then refreezing slowly in a domestic freezer deteriorates the product considerably.
All frozen food for sale is required to be kept constantly below -18 deg before sale but this does not apply to pet food.