The key part of the 'no old threads' rule is that it only applies in the vast majority of cases where old threads get resurrected for abosolutely no reason: some jackass wants to increase his post count by talking to the long dead or some new person doesn't realize he's scrolled way way back... it's perfectly okay to respond to an old thread if you have some new information on the topic. Replying to an old thread about the Vesuvius' specifications because you found a reference to another mass driver battery would be good -- reply to an old thread about whether or not people like rock music toio inform everyone that yes, you still do like rock music, would be bad.