I'm at 145 hours and I'm starting to feel the same way. I feel like I've done all the major quest content that is relevant to my character (didn't do the civil war yet, or any 'evil' content like most of the Daedric stuff and the Thieve's guild/Dark Brotherhood). But I feel like I've done pretty much everything. I've only been to 78/160 dungeons though, so maybe I will try clearing out more dungeons? I dunno. I'm patiently waiting for DLC to come out.
park that character until later and start a new one, since, it sounds like your playing to grind it out. finish the character that does everything and hits every dungeon for way later after you've roleplayed a few.
one of things i learned a long time ago was to limit the number of hours for any one character. and, learn how to better roleplay a character in a rpg game!
since i've recently started skyrim i now have a nord warrior loyalist-type, a cat thief/assassin, and, dead is dead character save-files. i play whichever one suits me at the time, play accordingly, and have serious fun.