It’s worth it to keep reporting these sites, even if they don’t all come down quickly, and even though more are added daily. The end result will hopefully be that google will want to preserve the integrity of their serps and begin to work on a new algo that will render old domain spaming useless.
I think google puts far too much emphasis on age of a site, anyway. While it is (was?) a useful guideline for determining a website’s worth, it’s no longer as accurate as it once was, thanks to blackhat exploitations.