This is a very bad idea! If you want to know one of the reasons why StackOverflow sucks it is because they shut down communication by freezing threads that appear to have a solution.
Just because you think you have a solution to a problem does not mean that years later someone won't come up with a much better or simpler solution. To deny people the ability to add to a thread years later is restricting the free exchange of ideas.
If your reasoning is that we should freeze old threads, because no one will see them, then why not simply delete the old threads? I mean, why stop there? If nobody is going to see them anyway? Right?
And what specific problem are we trying to solve with deleting or freezing old threads? Is PerlMonks running out of storage space? Are we afraid that somebody will revive an old thread? Why is that a bad thing? Why shouldn't someone come along and add an idea that no one has thought about?