Not quite sure I understand...Why would the case files end?
At the time, various sources stated it was a 13-volume series, most likely down to issues with printing at the time, and Dredd's shift to full colour. Back then, remember the el-chunky volumes were b+w only. IIRC, it was Nemesis 3 that introduced the b+w/colour mix, as printing costs dropped. (There were also discussions about what would be done with the Meg content, when it got to that point.)