Ajd_King posted... However, with the Radiant AI system, quests may continue being given out permanently.
That is neither what the Radiant AI system is about, or capable of doing.
As for time to completion it's been said anywhere between 20-35 hours. But it will vary wildly I mean how quickly do you want to complete it? If you fast travel everywhere, skip dialogue and run through every main quest then I wouldn't be surprised to see it over in under 20 hours. Saying how long the main quest is in an ES game strikes me as being "How long is a piece of string", however long you make it.
I'm not crazy, i'm psychotic. There's a difference.