My mother in law cleaned out her mothers freezer a couple years back (she has had dementia for some time now) and found buried in the back a package of hamburger in butchers wrap with an attached hand written receipt from 1976. There were also some steaks in similar packaging right next to it but no date. When they opened it up, they said the hamburger looked like some sort of diseased brain. They thawed it out of curiosity and they said it had a foul, most unusual odor. They tried boiling it to serve to the dogs and the whole house smelled so bad they tossed it instead and then tried getting the smell out of the house.
Now, that said...you have to wonder if, and how many, power outages there might have been in that house since 1976, and did she properly preserve the meat during those power outages? So was it bad from age, or from improper storage, or all of the above?