Personally, I rarely answer the same question on both boards. I just ignore it the second time I see it. Unless, I think of something else I'd like to add. I just figure its up to the person answering the question to read every board that they posted it on.
And, for those of you who dont know, when you make a post, there is a selection to have an email notification sent to you every time someone posts to that thread...........that way, if it is a question that was really important to you, you will be notified immediately when someone responds to it.