“But on the other hand, how do you acco …

“But on the other hand, how do you account for pre-B5 primetime serials like Dallas?”

It never even occurred to me to think of serials and soap operas as having a story arc in the sense that B5 does. Yes, they have an ongoing plot, but it’s a meandering, unplanned one that accumulates inconsistencies until they have to be corrected through retconning or a complete reboot (the infamous “Bobby in the shower” scene).

There’s more to a story arc than just having a story that spans multiple episodes. The movie serials of the 1930s did that, but they didn’t resemble B5 in any meaningful way. They didn’t have B5’s dramatic structure; they were just a series of set pieces ending in cliffhangers.

As for soap operas like Dallas, they have the make-it-up-as-you-go problem that was discussed earlier. A proper B5-style story arc requires that you have some idea where you are going. You don’t have to have the entire series planned out in advance, but you should certainly know how it’s going to end and approximately what path it will follow to get there. Soap operas never do this.