It doesn't require entire episodes to follow up on past worlds:
Originally Posted by hlndncr
- It can be as simple as a couple of lines of dialoge: "Isn't this a cool new medical device the Orbanians designed? Yeah, the exchange program is working well."
- It can be a ten-second clip of another world's ambassador ending a conversation and leaving the briefing room, before the current story's briefing gets underway.
For this episode, Scorched Earth, I would have enjoyed a few lines of dialogue about the possibility of future relations with the Ganmere:
Daniel: We'd like to get to know the Ganmere after they're re-established.
Lotan: The Ganmere will contact you in time. They'll be grateful that you found a way for their world to be re-born without destroying another people.
Daniel: How long will the terra-forming take?
Lotan: Many, many years.
Ah, so now I know not to expect any follow-up, and there's a good reason as well.