My farrier says the horse's hoof will tell him if they need shoes or not. My three do not, but there are other horses he shoes regularly. I have hard, stony ground in the corrals, and they normally go about 10 weeks between trimmings. They went 12 this last time because he was hard to get hold of, and only 1 of the 3 was noticeably long.
Mia & I chatting at the corral: