Just keep advancing the world events around the players.
IMC, the players range 33rd to 36th level after 3+ years of playing and still have a lot of problems in the world they want to solve that just going in to kick butt wouldn't work since....
They have kingdoms with evil tyrants to dispose, but don't have the resources to face thier armies dedicated to the god of war.
They have divine chosens running around stirring up trouble,
Gods on the verge of coming to the material realm and fight it out and kill each other that they are trying to stop.
They have places that house hordes of powerful undead to clean out that haven't had chance to get too.
They have a 400+ year old powerful BBEG out there behind a lot of stuff, that killed the elven royal family (his own kin) and tried to destroy thier home island and they want to take him down, but he has a lot power, influence, knowledge and backing that they are just now getting, besides they can't find him yet, and only one character met him once, briefly.
They have Quests to complete for thier gods, themselves, or just for the hell of it.
They have artifacts to destroy, or recover.
Lost (thought dead) gods to find and free, or in some cases find a way to free those that they have found. Or just learning these Gods ever existed and the world needs them back.
Demons, Devils, or other nasty outsiders out trying to setup permanent bases and gates on the material world to find and shut down.
All of this and more in the shadows that they still have to learn, and we still haven't started plane hopping. Of course they are meeting other powerful NPC adventuring groups and setting up alliances but they move a whole lot slower than the bad guys do, especially since the bad guys have been going at it for while before the players ever got started in the big league field.
Just a little light adventuring in my homebrew.
RD