Skyrim is a completionist's nightmare.
I'm over 110 hours in and I haven't even gone up to High Hrothgar in the main quest-line yet. I've just been dicking around doing all of the side-quests in the holds. I actually have a pattern in that I go to one hold at a time and do all of the side-quests there before moving on to the next hold. First I did Whiterun, then Falkreath, and now I'm in The Rift, and I think next is either The Reach or Eastmarch.
Sometimes, you'll pass random guards and they'll remark, "I wonder what the Dragonborn does when they're summoned by the Greybeards"
...To which I'd respond, "If that Dragonborn happens to be me, then they fuck around for several months performing fetch quest for random strangers and becoming the supreme leader of every guild in the entire country."
Fuck the Greybeards, they can wait. I have 50 more random caves full of bandits to kill so I can loot all their shit and sell it off to merchants.