Like any bow wood, the longer(to an extent) the better. I bought a stave from Yazoo's Dad at Hickory NC 2 years ago that was cut May 8. The shoot was at the end of May and I had a 60" bendy handle static recurve built and shot in a month later. That bow developed frets and I am convinced that it hadn't been seasoned long enough(or it could have been my tillering
) I know folks that have been successful with quick drying osage.
You can reduce a green osage stave to floor tiller stage, seal the back and let it dry well without adversely affecting the stave. It will dry quicker that way. However, there is a big difference between a dry stave and a seasoned stave. Seasoned staves fair better as bows.IMO