Bat dungeons should decay

[Sevenless]

A bunch of bat dungeons get spawned at world start, but after that the spawn rate slows to a crawl. Since dungeons seem to have "population caps", the best theory I've heard is that bat dungeons get spawned in noobie/hermit mines and nobody ever finds them as a result. Could we make them decay over time? It's not like bee/ant dungeons where you can actually wander around and find them.

(this is of course based on my understanding of the mechanic behind their spawning)