Canned food stays 'good' nearly indefinitely freeze dried or not...but eventually the vitamins and proteins and stuff that make the food what it is break down making is less nutritious and less delicious.

In an emergency situation any food will taste good if it's the only food there is. If I'm ever trapped in my home and need to eat, I'll be eating the flour and corn starch raw before I start starving myself. If I were hungry enough, I'm sure it would taste fantastic.