Welcome to Morrowind man.
The only game in my recollection that claimed over 700 hours of gametime, spread across several years: playing it a few months, taking a few months break and do other games, return and restart.
Its still in my opinion one of the best RPG's out there for its sheer size, characters, customizibility and challenge - for mage characters at least
I remember my first time playing that as a mage, being asked by the fighters guild to fetch a Dwemer box from a ruin outside of town and running into a NPC on a bridge that came at me with his skeleton summons and conjured weapons, having my butt kicked numerous times since I was poor and had such a limited selection of spells.
Fun times.