Following yesterday's mention of his Rule of Eight — an observation relating to the survival rates for independent publishers whose lines expanded quickly — Marc Patten wrote to remind me of an important nuance: "If memory serves, I think the 'Rule of 8' stemmed from the concept of new companies with some sort of shared universe concept, rather than just number of titles."
Thus, the eight-monthly-title barrier he perceived would not necessarily apply to publishers with differentiated lines. Dark Horse and Image both had mini-universes (Dark Horse with "Comics Greatest World" and Image with its families of studio titles), but in either case no one shared-universe sub-line accounted for more than half the publisher's output.
But when it comes to firms where the majority of the publisher's business relied on a shared universe, eight monthly titles appears to have been more of a red line, historically: Valiant/Acclaim, Tekno•Comix, and CrossGen are among the companies that vanished after crossing it. "There is still no shared-universe line that has managed to survive outside of Marvel/DC to date as far as I know," Patten says, beyond that eight-monthly limit.
There are likely exceptions to be argued with the formulation, but the larger point is this: the expansion seen in middle-tier companies today is in some ways different from the expansion seen in the 1990s. Publisher lines are more differentiated internally, and less reliant upon individual customers who buy everything. Comics have become, like many other media, more grazer-friendly.