But if I were Hel, I would have ordered him to watch everything, just to be sure not to miss anything important.
I think that while watching single memories doesn't need time, watching a lot of them needs some time. And Durkon has a role in watching memories, as Durkula said that he'll need to speak with him until he has watched everything at least once. And that Durkon tried to fight against the vampire, trying not to give him, for example, Roy's name.