Well, I'm not an expert on this but I have found that much depends on which choice of mix you have and what the environmental conditions are like.
If you think of moss as a sponge or wet rag which sits in a damp warm bucket with little or no air movement, you might be able to understand much of what happens with potting mixes.
Then, think of what happens after rinsing out the old sponge or rag with clean water and letting it dry out a bit with a gentle breeze in the sun.
With our potting mix, its not just about humidity, air movement and adding nutrients. It actually a cycle which will balance everything.