I put in about 150 hours or so on my first play through, I'm only about 10-15 in on my 2nd charcter and I'm level 17 I think already. It just depends if you like to explore EVERYTHING. My first play through I did as much as possible, but tried to stay away from finishing the main quest, and it seemed like I'd easily eclipse 300 hours if I finished the game on that one. But halfway through I wanted different perks, and wished I did things differently, so I suspect once u've played through, or mostly through, once, you'll knock down the 200-300, sometimes even 400 hours down to 100-200 based off efficiency alone.
and Ive stopped to stare @ the night sky more than once, how can you not.

. Without this topic my Skyrim time would have not been as high.