Window ac unit question?

I just bought a new LG 8,000 btu window ac. Installed it and it seems to work fine so far and cools well. My question is I can see a plate of styrofoam screwed inside behind the blower fan where the cold air comes out and where it borders the outside. Is styrofoam durable for window AC's? My unit came with a 5 yr guarantee. Does it insulate better and hold up ok?