For best flavor, you should replace your herbs and spices every six months. I replace mine in the spring and fall when the clocks change
I love Amy's frozen dinners, particularly the cheese enchilada dinner
I was really surprised, though, to read an article in a recent issue of Nutrition Action Newsletter that basically said some of these natural frozen dinners may not be any better than their highly processed clones at the supermarket.
The article can be found at
http://www.cspinet.org/nah/06_05/frozenpromises.pdf (It's a pdf file)
In particular, they mentioned the higher than usual amount of saturated fats in some of the dinners. They also pointed out that many Cedarlane dinners list the nutrition data, which seems reasonably balanced, until you learn that each package actually contains two servings, so you should double what the lable says. Who eats half of a frozen dinner?
They are the same size as Lean Cuisine or other single serving dinners.