Set aside that we can clean PVP manually. I was thinking about this...what if there will be some dust-storms and no players to clean them? I see it this way: PVP will get more and more dirty. After it reaches 50% they all shut-down, system drawns 10% energy from the batteries, and the PVP restarts with 90% cleanenes. If players want them to be cleaner, they will have to come and clean them individually.