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You are right. If the thread is older than two week it's better to make a new one, because the content of the thread you are posting into might not be up to date. Also it keeps the forums fresh with new threads. It's actually explained in the community rules :
"Before posting a comment please make sure that the thread you’re going to post in isn't already dead. Bringing back old threads isn't something appreciated as they can contain very outdated information. Also, we want to keep the forums sustained with fresh threads most of the time. If you see that one thread hasn’t received any comments for two weeks, please make a new one. We can accept a thread necro from time to time if you are the OP, depending on what it is."