I always try to read the whole thread--usually somebody has already contributed what I was about to say, and said it better, accounting for my low ranking for having been around as long as I have; I try to add someting substantive instead of a "me too" so the discussion stays fertile and concise.

I don't mind old threads being resurrected when someone has new information to offer--they may not have been around at the original discussion, and it shows their interest that they root around for all our previous wisdom. In fact, would that more people did such research before bring ing up a question that has been thoroughly beaten to a pulp.