A Finite Series

Standard practice with a comic that sells well is to continue selling it indefinitely through multiple changes both of creative team and of plot direction, thus generating, over time, thousands of pages of ephemeral quantity at the expense of enduring quality. When Swamp Thing  was scheduled for cancellation, Alan Moore took over the writing, reinterpreted the title character from mud monster to plant elemental and transformed the series into a top-selling title.

When Moore had finished the story that he had to tell, he gave the characters a happy ending and it is easy to stop reading at that point. His entire run has been collected and thus saved from transience. Rick Veitch continued the series well but differently. However, it had its ups and downs after that, ending on a high point with Mark Millar but revived a few times since then.

Neil Gaiman initiated a new Sandman series and insisted on it ending when he had finished the story that he had to tell. However, it has had several off-shoots, notably Mike Carey's Lucifer, also collected in its entirety, and, in any case, continues to sell better as collected editions. Because The Sandman is a lengthy but finite series, it has a comprehensible structure that can be mentally mapped:

Preludes And Nocturnes (8 issues) + The Doll's House (8) + Dream Country (4) = 20 issues;
Season Of Mists (8) + (Distant Mirrors - "Ramadan" (3)) + A Game Of You (6) + Convergence (3) = 20;
Brief Lives (9) + "Ramadan" = 10;
Worlds' End (6) + The Kindly Ones (13) + The Wake (6) = 25;
Total = 75.