As I’ve been studying Stargate SG-1 and Stargate Atlantis, I’ve been paying attention to how the episodes use story threads. It happens in one of two ways; The writers either create a new thread, or pick up where an old thread left off. Executive Producer Brad Wright in a GateWorld interview;

“That’s what Atlantis did well in that we created a universe wherein multiple storylines could be born and take place and spread and grow. Those are the lessons we learned building SG-1 in the first place. While it started with mythology at its root, very early on, by mid-way through Season Three and [the] beginning of Season Four, we had created enough of our own mythology that wasn’t rooted in the culture of “X.”"

One of the strengths of the series is its ability to remain fresh after so many seasons, and the best I can determine is that their ability to do this relies heavily upon those open threads. You can resolve a thread with a villain being killed… or so it appears. But maybe they are revived, cloned, take a new body, or found a way to escape at the last second that the hero didn’t know about. While this is standard fare, the more interesting type of open thread is when an episode features a new discovery: New technology, ancient artifact, riddles constructed out of alien languages. The characters never truly know the full story. A pillar inscribed with text may lead to certain discoveries in one episode, but the interpretation of that finding may change or evolve in drastic new ways in a later episode.

It is safe to say that the SG-1 writers did not have entire story arcs across multiple seasons planned out in advance. So then how did they make it seem like they did plan it? They left themselves enough open threads, and had confidence in their own abilities to deliver on those open threads when the time came. Making yourself seem like a master story arc planner is just a matter of leaving yourself enough opportunities to create that illusion through future stories.