A lot of comic books function by appearing in compilations first.
nonwithstanding, authors with moderate popularity will sometimes put 'breaks' between major arcs not just for downtime, but in case the story ends for whatever reason and they can end them in a somewhat satisfying manner. Sometimes this is an organic part of the storyline, the author fishing for more money, or the author working on another story.
Unless of course, the people funding said storyline would really like them to continue. This becomes a big problem because sometimes the author is 'forced' to stretch an idea, making very good marks in the road to running too long
because the author is out of ideas and has to start coming up with very different ones. Occasionally an older idea that provided 'closure' is ignored or reversed to allow for this.
Naturally, these stories end up running quite long. Fans sometimes use them in a suggestion of relative decline, even if the story itself remained decent.