This all seems to be based around the assumption that everyone comes here to ask a question, then someone gives them the answer.
The problem I envisage is if someone starts some project and asks advice on it, then wants to give an update a year or so later but finds they can't because it's been automatically locked because newbies had been resurrecting old threads.
Also I've been on computer forums which I've found after googling a problem, had a similar problem and I've really wanted to just post something like 'I've got the same problem. I've tried all that but it still doesn't work' without having to explain the problem again, and have everyone suggest all the possible solutions which I've already tried.
Maybe a suitable compromise could be if when a thread is started there is option to flag it as a 'question' which can then be locked after 6 months' inactivity?
Alternatively maybe the option at the end of a thread could redirect users to the new threads instead of similar previous threads?