We keep older threads as reference, but locked, on the idea that its better to have people start a new thread or find a more recent discussion to add to rather than restart a really old thread.
Older threads are locked automatically, and eventually deleted. Do you find a problem with there being too many old threads when using search? We are looking at reducing the number of displayed topics a little.
I personally have never used the searches and don't know why I ever would. I don't see why we have a hundred-some pages of locked threads that just sit there taking up space. Today, just for fun, I looked at page 137 of the Design Talk forum and was quite surprised to see that one of the topics was posted by Henry Ford himself, outlining the finer points of the Model T design theory.
We have had some problems recently with bandwidth usage (due to lots of attached sketches in the Sketch Groups forum), but disk space isnt a problem... We'd only need to delete older stuff if it gets hard to find things due to too many topics.
Search can be very useful if you are looking for specifics such as a designers name, looking for software or services, where to buy Vellum paper, etc...
As I said, I've never tried a sketch, so I wouldn't know, but it sounds like there's no reason to delete Henry's post any time soon. Maybe we should do a search for a quote from Enzo...