Personally, I feel that too many board battles running simultaneously will dilute the content of existing ones. I know that I won't have the time to read up on and then post quality replies to numerous board battles. Furthermore, every board battle needs a host, and hosting can be a very time-intensive business as well.
I would suspect that if we have too many battles running simultaneously, we'd either end up with having only a small number of dedicated members in each one, or the quality of posts in each battle would likely suffer. We just haven't got the number of members needed to realistically run a bunch of decent-sized battles simultaneously.