I don't. Highest level I've ever got a character was 41, and that was my neccecary do-the-main-quest first character.

Twice i had a character that did all the quest i wanted to do
One lvl 58warrior paladin and one lvl 51 rogue type charecter , i just retired them hoping fhat a future dlc can bring them back in game

I just make a new charcter , mostly a new build/type and start all over but with a different approach

Realize how much of my life I've wasted.

My endgame is quests, since I spend the first major part of the playthrough just plundering dungeons and leveling up.

It would be cool if Bethesda could have added a few post ending challenges, just a couple of super high level dungeons would do, I'd have even been happy for some kind of celebration in Whiterun, anything really, the game felt a bit strange after returning from Sovngarde, not really many people to talk to about your success.

This....and then this again...and again and again and again...

That, certainly if I was sat down for a while.

With the console version I just gave up. Nothing else to do. Now, the PC version's different. With the ability to do your own mods I've become ambitious. When I eventually start the PC version I intend to play to the end of the vanilla quest using graphic, magical and character mods, then use the end of the vanilla game as a "coming of age" for my Dragonborn, in the same context as Arthur drawing the Sword in the Stone. From then on I'll be creating new stories, quests and challenges for him, one of which will be the challenge of building and defending his own "Camelot". I've already decided on a location for building my fortress, which will be situated and an annexed hold in Skyrim. Eventually I'm hoping to add to the map with other parts of Tamriel as well, and maybe even take on the Empire!

I go find mods that add territory and/or change the way the game is played.

I have yet to even dent all the quests with 1 character as i switch between 2 different characters...i dont see my game ending anytime soon

Never reached an "endgame" as you call it.

Endgame? What's that then?

I'm a thousand plus hours in with just one character, I can always find something to do.