Creating more specific forums creates dillution. This is a good thing if your main forum gets so much traffic that a day's worth of postings cannot fit on two pages, but if you dillute when it doesn't need it you end up losing that effective (if only occasionally volatile) mix that makes the site work.

Even Michelangelo had to look at the ceiling of the Sistine Chapel and decide that it was as good as it was going to get. Don't mess with a working combination, Bob. Just figure out a way to add another day to April.