Question
I have a large bale of (organic) peat moss. I'm just wondering will it break down because you said it'll break down over time.
More information:
~it is pretty dry
~stored under a wooden shed outdoors
~has a 6 inch hole on it

Answer
If the peat is dry, it'll last indefinitely.  It'll start to decompose further when it's wet.  If you see a hole in the bag and you don't plan on using the peat soon, just tape it up or cover the bale with a tarp to prevent water from seeping in.

Good growing!
Jacob Farin