I'm 43 hours in and I probably am close to uncovering only 1/3 of the map. I've only seen 3 major holds (Whiterun, Markarth, Riften), haven't even explored the others yet. The game is massive. The amount of content is ridiculous. I'm even still finding new quests in Whiterun where I spend most of my time. New things are constantly popping up, such as couriers, new rumors at the tavern, etc. It's really nuts how much content is crammed into this game. If the other holds have similar amounts of content, I'll be playing this game forever.