~snip~
Yeah, those are really annoying. They usually bump threads just to post some generic crap in and within a matter of hours there can be pages of spam to remove and it's incredibly tedious to do so.
Even though necro posts aren't technically breaking any rules, in most cases the ones who are necro posting are ,like what you said, posting generic crap, and most of this threads that are necro bumped are most likely worthless and easy to answer threads that is why the spam will be a lot in a short span of time. I just hope that there is a system where old threads that died already are not bumped back up to the first page of the section, as this will also help you and the other mods on your work cleaning up the forum.