Hey Ranger,
Every horn I have has had a shot of Raid or Bengal sprayed inside, and the outside wiped with the same on a rag.
Those beetles love to crawl inside a horn and lay eggs, and the babies hatch out and start eating. Keep a stopper firmly in place on all horns.
Otherwise, horns are pretty tough. Keep them out in the light as was noted, and in the same climate you'd live in.
Hope this helps. God Bless, Marc