I've long thought that adding to old threads (versus starting duplicate threads) is what our forum community preferred.
Think of all the times a forum member has asked a question, and the response has been "this has been discussed before", and/or "search is your friend".
I thought that at least part of the reason is the possibility that someone looking for an answer is going to find it more quickly because the answer has already been posted, even if it was in the distant past, and because of the advantage of having all discussion on a topic together.
Of course the problem is that a topic may be so broad and the thread may be so long that it's unwieldy to read or use, so some may start to ignore it, as was pointed out.
But if the discussion is on a narrow topic (for example, how to program the star button) IMO it's advantageous to have all discussion within a single thread.
'16 Turbo,Sapphire,Black Leather Int/Sport Classics/Window Trim/Roof Rails/Xenons, PDLS+,Tinted Tailights,Sport Design,PSE/PTV/AS/SC/ACC,Burmester,Prem/Comfort Lighting Packages,Leather Dashboard Trim,Seat Console,Steering Column,Rear View Mirror and Sun Visors, Leather Interior Trim in Pebble, Pebble Seatbelts, Headrest Crests, Armrest Logo, White Dials/SC Clock, Alum Fuel Cap, Spt Design Mirrors, Surround, Connect/Online Services,Painted Key,Leather Keypouch,Illum Door Sills