Longer is better, or they won't want to stay straight, but it depends on how dry it is. For me, when the bark starts to wrinkle and go dark, they should be good. Also, when I hit two together and hear a sharp, musical ringing sound instead of the dull clunk they make when they are green, then you can tell they are ready. If you put them in the back window of a car, you can probably get them there in a month, easy. Straighten them every few weeks while they are green, and bundle them tight, and it will make your job easier when it is time to do the final work.