When is one ready to graduate?

Katsouleas reminded me of a very simple answer. You are ready to leave the phd behind when you reach a point at which yourself can decide what to do next. That means that when you read , listen or study something, then ideas come into your mind as to what you can do with it ('Oh, we could do this and we could investigate that and make this parameter this way and maybe do it with these tools' etc). Right now I can only do that with the specific problem that I am working on - I know where to look and what needs to be solved and what needs attention. But I don't have a clue for anything else around me, which means I have a long way to go still.