Well, I can imagine myself as author of a question. I asked for a problem and then read what somebody thinks about it. Does it need to answer for the each suggestion? I do not sure. Ofcoz I may say "thank you", "i`ll look on it" etc --- but: does it make traffic lower?
Another side is that as a rule, problem is not original one. After some months, another person will visit the forum and do search: wow, there are a lot of answers on my question!
From another side, I understand you - people visit forum and read-and-read same threads with alot of answers. But... Whatta hell a forum is for? Is it strong system: a question - good answer - close? No discusion? I doubt about such way. An idea: you as moderator may create a sub-list of threads which are overloaded and/or out-of-date. Or even better - original poster of a question should have a possibility to cancel/continue own thread: set it as active, close it, move to old list etc... What do you think?
Good days!