Board Thread:General Discussion/@comment-74.34.58.150-20140102222045/@comment-4057437-20140107044520

They take longer if all the side quests and (Dawnguard) skill trees are completed. Dawnguard also must be done twice, once for each faction, to really have done all of it. Riding five dragons (the first one doesn't count), can take a while as well, depending on how often dragons spawn nearby.