Funny thing is, on some of the shows that are people's favorites, you get the sense that life simply went on a lot the same for every one of the characters after the show ended, we just didn't get to see it.
At the end of Cheers, Sam shuts down the bar for the night at closing time after everyone's left (someone shows up at the door and tries to get in after hours but he's told, "sorry, we're closed."). But you know he's going to open up again at the usual time the next day, with the usual gang of regulars filtering in at the usual time, and it'll keep going for years to come. We just won't see it.
Same thing for other long-running comedies, any of them that didn't neatly wrap up the narrative in a finale like Happy Days did, should probably be assumed to just keep going on with their characters slowly aging and life slowly changing at a real-time pace.
One which COULD have been interesting to see as an update and follow-up would have been Seinfeld, whose main characters we last saw in the Latham, MA jail. What do they do when they go back to NYC and resume their lives? What craziness do they get into? You can pretty much figure that Jerry hits the standup circuit again and maybe finally gets that sitcom or cable talk show he wanted...Elaine marries, has a kid, divorces and lives a life a lot like Old Christine (so we got our answer to that part of the story on TV, only on a different network)...George probably moves back in with his parents and repeats the cycle of futility, probably in the front office of the Mets where his decisions help mire the team in its current mediocrity...and Kramer tries standup comedy and creates a scandal with a politically incorrect routine. The actors themselves did a reunion, playing themselves, on Larry David's Curb Your Enthusiasm..There was actually some talk of a Seinfeld reunion show, either a two-hour TV special, miniseries or theatrical filml, to pick up the story at some point after the characters are released. Jerry said he'd do it if he or Larry David could come up with a good enough story line, and hasn't ever ruled it out even today. Guess they just haven't come up with a story yet, that makes them want to give it a shot...