I use only the wood chippings for the last few years....still working fine even tho the 'dirt' is showing thru in many places. Could be that 'dirt' still has much wood in it.
Run is 8 x 50. I have 13 birds right now but used to have as many as ~30 in the spring and ~18 in the winter.
https://www.backyardchickens.com/articles/aarts-coop-page.65912/
Yes. It turns into 'dirt' eventually.
I haven't done anything to my run in 10 years, except add a bit more wood chippings if things get stinky. Don't need a thick layer of wood chippings, I keep mine about 1-3".
I sift the poops out of the thin layer of PDZ on the boards every day and put it into a kitty litter bucket. When 3 buckets are full I take to my friends who have copious gardens and composting facilities. They empty the buckets and bring them back. Good deal for both of us and we've been doing...