This is necessary so that the immediate excitement surrounding the thread can die down, allowing it to be more objectively evaluated on "yes, this is a worthy and timeless thread" versus "no, although this was a cool thread at the time, it is nothing special six months later".
One way to tell if a thread is a classic is by whether people are still referencing it, or posts covered in it, in a non-"this must be in the classics" manner, months later.
I direct you to the allcaps thread being included well within this timeline and hasn't been referenced since in other threads. (Except for resulting in an immediate splitlock.) Many of the original threads are of dubious relevance to anything with most of the posters in them leaving back when I joined, or before, and I've been here...jesus, seven years? Longer? They never managed to meet the reference criteria either. Any cultural impact or influence burned out ages ago.
Also even by this standard you've clearly failed to include multiple threads which met the criteria and have arguably contributed far more than the majority of the threads currently in the archive, such as Kazan's being lured into arguing against the Clangers which got referenced for two or three years after, or Goob Hates Us All, which
still gets the occasional reference.
There are number of worthy threads in the Classics section. The fact that there haven't been any new ones in two years has no bearing on that. And there's no policy that says we must continue to add threads to the Classics.
There's no policy that says we must keep the Classics either, and HLP has eliminated boards which are not maintained before. If you want to create some random project and just allow it to rapidly die off, well, that's pretty normal around here but it's still a remarkably dick thing to do.
Seriously, the Classics section wouldn't have passed muster as a hosted campaign. It'd be gone by now.
Keep in mind that every thread we add, no matter how worthy, will dilute the value of every thread in that section.
Maybe if you mean monetary value via enforced scarcity, but I'm hoping not. Otherwise, this is patently ridiculous. That's saying that every post causes HLP to continue its infinitely long approach to zero valuable content; every page of a book makes it worse; every time someone speaks it reduces the meaning of everything they have ever said. This is clearly not the case.