I did a full rewatch of SG1 a few years ago, and what surprised me is how instantly the show found its footing. If you watch the first and last season of any Trek show, you can see how the writing and characterization takes a while to settle into place. Character development is part of that, but it goes beyond that.
If you watch the first and last season of SG1, the writing has its footing nailed down immediately. Not many shows find their footing so effortlessly.
That may have been helped by the fact that SG-1 got the green light for 4 full seasons right off the bat, so it gave showrunners the opportunity to write a cohesive and comprehensive story which really laid the foundation for the franchise after the original movie.
I don't have a source handy, but I recall reading about that many years ago.
Wikipedia says they were picked up for 2 seasons, totaling 44 episodes. So while it's not 4 seasons, that's still a lot of stability for a show to start with. That would explain how they felt comfortable enough to plan ahead.
If you watch the first and last season of SG1, the writing has its footing nailed down immediately. Not many shows find their footing so effortlessly.