This is true, but I've noticed over the last few weeks as I get more and more megathreads locked, that old ones just pop up in their place. Old threads that have 30+ pages but have had no replies for a month or more are bumped with insubstantial spam to the front page, and then the whole spam cycle starts again as shitposters flood these threads with their one liners. You can report them and they will get locked within a day or two, but not before another 5+ pages of shit have been added on to them, and then another old thread is simply bumped and we start again. With literally thousands of old threads available to be bumped, there's not way to keep on top of them all without board specific mods who can clamp down on this sort of thing within minutes of it happening.