How to keep a story going

Something I have been wondering while looking at Star Wars The Clone Wars. We have all these events, going into the fifth season now, happening to the central cast of characters, as well as the movies, novels, games and various off shoots. What I'm wondering is how they can keep the story going while making it credible.

To demonstrate what I mean let's have a look at Under Belly. The first season was on the Melbourne gangland wars, narrated by one of the characters, Jaquei James. She would then go on to narrate the other stories such as the Calabrian mafia, Kings Cross, the Sill Miller murders, each had a different cast. It's reasonable that Steve Owen and Jaquei James would investigate Carl Williams, but not Terry Clark and Bob Trimbolie, or George Freeman and John Imbraham. So how do writers get us to suspend our disbelief that Anakin and Ashoka have been involved in everything they have been involved in?

Star Wars lost rights to the claim of credibility long ago.

Yeah, heh, okay. A better example might be Blue Heelers, if you don't mind me bringing it up all the time. The series went for some thirteen years and five hundred episodes, and as the series progressed the crime, serious crime, did as well. It went from shooting a dog because it was considered vicious and talking down a farmer with a gun to drug runners, serial killers, pedophiles and corrupt cops, all within the setting of Mount Thomas, a town of about ten thousand and all involving the same cast. How does a writer be able to have this while still maintaining Willing Suspension of Disbelief?

They aren't really A story, there a bunch of stories with reoccurring elements that take place within a certain time frame. Most series keep things fresh through character development, world-building or playing with the formula after it's been established.

That's probably the best I can explain it.