For me, it's when I can put three arrows in the kill at thirty yards from a variety of shooting positions.
For you it may be different.
Most of my hunting is white tail hunting from an elevated stand. Most shots are inside of twenty yards, but there is an opportunity for longer shots out to thirty yards.
You need to honestly evaluate your hunting situation/scenario and determine what you need to be able to do when you are faced with a shot.
I also think that it is more important to know what you are capable of, rather than knowing when you are ready. In other words, if you know that you are driving tacks at twenty yards, but can't hit the broad side of a barn from thirty, don't take shots at thirty yards no matter how tempted you are.