There's a lot of very good information in many of the old threads. You have someone who's an active poster for a certain period of time and has expertise in a particular area, so during that time there's a lot of discussion and information available in that area; but at another time there may well be no one around who's focused on that particular range of subject matter, so it doesn't get discussed. The constantly changing membership on sites like this means that sometimes the older threads have coverage that none of the recent ones do, just because of who was interested in what, when.
Another good reason for looking at older threads is just the flip side of what I was just saying: sometimes current topics turn out to have been covered in gory detail two, three or four years ago, and if you know what's going on in the older threads, sometimes you can avoid reinventing the wheel.
What's kind of funny is to see how certain topics never go out of style, particularly of the Horror Stories variety... Ashida Kim and Frank Dux have a small encyclopædia's worth of coverage each... :lol: