Start with no more than three boards. Grow the board list proportionally to the square root of your (active) community size. Otherwise you spread conversation

Start with no more than three boards. Grow the board list proportionally to the square root of your (active) community size. Otherwise you spread conversation too thin and you community feels like a ghost town. A rule of thumb I like is to split a board when someone checking in daily wouldn't be able to easily locate the conversations they participated in yesterday. On a paginated bulletin board that would be when you regularly get daily activity in more threads than your page size.