It is definitely well over 30 hours of gameplay, but it is not all linear gameplay (See most modern games now ~10 hour main quest line) 

*Spoilers* Just got a dremora butler to carry stuff for me when im tired, sweet!

1,200+ Edit: I should add that I have all the expansions and have been playing off and on since release on Xbox.

*Spoilers* Any reports on Black Book powers?  So far I have unlocked the ability to make my Frost breath freeze people solid as well (for a good 10seconds or so I may add), 10% increase in effectiveness of all combat skills, and the ability to NOT HURT ANY FOLLOWER IN COMBAT EVERRRRRRRR WOOT! (With Weapons, shouts, or magic!). I kind of wish I picked the Fus Ro Dah's perk though because it says it increased the damage and had a chance to DISINTEGRATE enemies. 

Yup! *Spoilers* If you go to Skall Village as part of the main quest line he mentions that cleansing (breaking) the stones it will weaken Miraak's power in your realm and delay his return.  If you do this and go to all of the available stones (You cannot do Tree they say because that one is located in his temple or something) you will be able to absorb dragon souls once again.  A few of them spawn several lurkers though so beware!  Bring a follower or bring a lot of potions if you are playing on a higher difficulty setting.