Brands and characters and franchises are easily mined for value with minimal marketing reinforcement. In a lot of cases they already have traction in the minds of at least one generation.

Keep something around long enough to have that generation introduce it to their children, you've successfully woven your franchises into the fabric of the culture and duped the entire world in to thinking Star Wars and fifty year old superheroes are interesting or relevant ad infinitum.

...I'm not bitter.

Well, it seems to have worked alright for James Bond, though there hasn't been a big gap between those films over the years. So while the actors pass the torch, most of the audience already knows the franchise.

On the subject of Star Trek, does the Abrams reboot count? It's meant to be the same characters, but Leonard Nimoy showed up to pass the torch to Zachary Quinto and the other young'uns, in a sense. I still love Star Trek '09 even if Into Darkness was a disaster, so I'd call that a successful attempt, if it counts. It's the only one I can think of.

Well, and Ghostbusters actually already tried it in the 90's with The Extreme Ghostbusters, where Egon, Janine, and Slimer were on hand to train and support a crew of new, totally radical ghostbusting twenty-somethings. I liked it well enough as a kid, but I haven't gone back to revisit it as an adult. Though even as a child my favorite story was the two-parter where Peter, Ray, and Winston came back.

Yeah I'll take Star Trek as one but it is so rooted in TV that it's not a pure example of what I'm thinking about.
But I'll give Star Trek that it did it well.

Star Wars seems to be heading down that road and like Ghostbusters I have a bad feeling about it.

One meta example a friend mentioned to me was ‘After Earth’ where Will Smith was going to pass the action hero torch to  Jaden. What a mess that turned out to be.