I've been playing MC on and off since beta 1.4 or 1.5. I've tried mod packs through custom launchers. I've tried my own collection of hand picked mods. I've tried a bunch of different things. However, at the end of the day, I find myself maintaining and playing the same world for as long as it is practical, with no mods, single player, survival, with LAN play.

While I am fully capable of updating mods, if they continue to be updated with MC releases, I've found that over the years, it can be a pain and adds complexity, if I'm playing the same world for a long length of time. (With some modded worlds in-between as a diversion.) For example, making sure that all my mods are the right version, for the right MC version, with the right Forge version, and with the right MC Patcher or Optifine version.

Here's what I've found:

MC Dungeon turns Minecraft into the Minecraft that I had envisioned being the future back when I had first started playing. It's a map editor that adds a variety of randomly generated dungeons to explore to your existing map.

It's not a mod. It's an external program that is exceptionally customizable, that will make Minecraft feel more like Skyrim or lord of The Rings.

It's been in development for years. The team that created it has a finely honed sense of aesthetics and adventure. Plus, again, it's highly configurable. You can restore/regenerate your dungeons as they are cached. You can add more dungeons as you reveal more map area in your seed.

Since it's not a mod, you don't have to worry about it breaking. (An exception being 1.9 loot tables for spawners and chests. However, MC Dungeon has a long history of updates.)

You simply run the external program on your save and adventure.

It's an epic mod. The dungeons are fun and well thought out. There's plenty of variety, it uses vanilla resources, it doesn't slow down your game, and includes some impressive details.

I cannot recommend this map editor/dungeon generator enough for SP survival.

There's also the Technic Platform/Tekkit launcher, but a lot my favorite mod packs seem perpetually stuck at release versions 1.5 - 1.7. You might also experience some slow-downs depending on your gaming computer and the mod pack.

But really, all you need is vanilla MC and MC Dungeon. If you don't want to explore and then generate dungeons, you can run Minecraft Land Generator after creating your world and the use MC Dungeon. This gives you a better sense of discovery and increases performance as new chunk generation is resource intensive.