So far, I haven't unpublished a hub. Maybe that's wrong, but they're like my babies. If I see a hub getting down to just above 60--say 61-63, I will look at it to see what I can improve. I'll revise it or try to put out some links to get more traffic and thus raise the score. Up to this point, none of my hubs have fallen below 60, and I'm satisfied with that.