I had one case of red mite under a broody (was awful - you couldn't miss it in those quantities, lots of tiny scurrying dots) and I binned all of that bedding plus the bedding I moved her onto while I was clearing up the coop. Didn't even want to keep it long enough to burn it! But I'm putting all the rest of the bedding onto the compost heap as normal if I've not seen any red mites from the other houses.
I'm gradually creosoting all of the poultry houses (as well as painting them all on the outside - all very pretty to look at now) and haven't seen any mites since. Mind you it's now all so dark, they'd be harder to spot so maybe I just deluded.
H