Seedcorn, I have few chickens and it is mostly "if it doesn't stink, they can go another month on it." So, their shavings gets plenty of chicken poop and it's pretty dry.
Then, those shavings are mixed with some real compostable stuff. Finally, I am happy to mix organic fertilizer into it. The ingredient listed are feather meal, meat meal, bone meal . . . in other words, they have used the
whole chicken in that fertilizer. Still, I can dig into that over a year later and still find plenty of recognizable wood! At that point, however, I don't worry about it.
Here is about what I did back when I got a truckload of shavings and the cleanest stable manure one could imagine. I was still using ammonium sulfate during those days, especially in my compost.
Horse Manure Management, Ohio State University (link) My experience was pre-internet but I must have used about the right mix because the shavings really disappeared by 18 months.
Steve