finished the main quest 2/3 times with different characters and classes. Built one final class that I'm going to essentially play most of the game with before bothering to complete it. Probably keep it going forever and not bother with the final parts of the main story.
Doesn't take long to do the main quests in fact.
One of my mates has done about 100+ hours of the game without initiating the first main quest part and thus has not even seen a random dragon attack anywhere at all. His character is pretty much levelled to the top with all (possible) perks unlocked. He's mental.