If you have something in the freezer for two years, how would you know, other than looks, if it was fit for human consumption?
Funny that you should ask this because today I spent the day giving the fridge and freezer a long overdue cleaning/clean-out. It was a very profitable day as I found a nice bottle of micro brew in the back.
http://www.health.state.mn.us/foodsafety/store/cold.html
Taking it out five days later was most unappealing. 
Being as I had Squirt, two cats in carriers, a Labrador, important papers and food for all of the above in a Camry, I wasn't thinking about the shrimp. :roll: