If you put a comment on a months-old post, don’t be surprised to find that I’ve deleted it.
At least until I get the plugin/code needed to close comments over a month old.
Of course, I doubt the people who are posting new comments on posts from November 17th will read this. But my regulars will, and can laugh at them.
Have you thought that sometimes maintaining an historical perspective to a post can be of use for future generations, er, to comment on? :-)