Like Eric, I've made a few bows of osage and yew that took virtually no set and lost no weight during shooting in, or with considerable use, and they weren't made or treated any differently than the other osage or yew bows I've made. I figured they were just exceptional pieces for reasons I may never know.
The osage bow that comes to mind is the one I've used the most, many thousands of arrows through it since '04, still stands straight unstrung, and it has actually gained a few pounds since then. The stave came from Ohio and has very thick rings and an exceptional early to latewood ratio. 66" ntn, 63# @ 28", less than 1 1/4" wide, and fully radiused belly.