In my game, we have multiple groups.
Each Arc contains sixteen sessions. That's 12 issues, an annual and a giant sized special. Sometimes there will be 17-18 if we get stonewalled or so, but then we switch to a different group and handle something else in the world. By keeping it fresh and then going back to old characters, we maintain the world, and it's been 29 years. Players come and go. We use a staggered experience point system so that high powered characters don't get a ton of XP for beating up Foxbat-level villains.
But the system works. And people are happy with it.