Yes you are correct but there is a difference between a circuit and the streams that are routed through the circuit. In vidalia you can see the circuit as the series of three node names, and the streams are underneath the circuits and look like this : dkn255hz262ypmii.onion:80 open (or connecting, or closed). If the circuit that is established is broken or closed, then you need to go through the introduction stage again. But if the streams are broken or closed or never open, the circuit stays open until it is inactive for a period of time. By opening new streams through the circuit, you make the circuit active again, even if the streams going through it never connect.