FWIW
No need to wait. I have made a finished bow less than three weeks from cutting the tree live. Same day work your stave down to a blank and heat with steam and straighten on a caul with 2" backset, let sit 24 hours. Work bow down to the point it looks ready to floor tiller and place in hot box/drying box for a week. Take it out and file with it a little at a time, storing back in the hot box or hot car in the sun when not being worked. After about 2 weeks you can tiller the bow, it may take some set when you do. Put it back on the caul (with about 2" backset) and heat toast the belly with a heat gun (Outlined my Marc St Loius in TBB vol IV on heat tempering). This will drive out most of the rest of the moisture, and stabilize the osage. Finish the bow. Viola! for those kids who just can't wait!