Yes, there's a detriment, to Mods and to users. With that much time to edit, let's say I open a topic called, I dunno, show your hands if you love evolution. And 500 people do so. Then -- because I am a prankster, I change the topic (which is a good 11 months old and long forgotten by most -- don't forget how fast things can fly by here because there is so much info) to show your hands if you believe in creationism.
I've just gotten 500 people to give support to my position. Now, you might dismiss that as being nothing, but this site is extremely well-optimized from an SEO perspective. Hence a future Creationist sees, aha, look at all the great Creationism topics!
And so -- while we have no problem with allowing both sides to post, of course -- the issue is that the Creationists' numbers are coming about due to false pretenses. It unfairly and incorrectly changes the character of the board. If I change my mind, I change my mind -- but in this case I've also forcibly changed 500 other people's minds, too.
Furthermore, if I get a job as an email marketer, what's to stop me from adding my spammy tagline to my old post? Then my company gets a boost -- and what appear to be 500 fans.
As Mods, we get the brunt of the complaints on the Help Desk for such nonsense, which of course means more work for us, and the membership can feel cheated by this kind of a cheap trick, as well they should feel.
Don't laugh and dismiss this -- it can happen although not necessarily on an 11-month scale.