Board Thread:Skyrim/@comment-110.174.122.151-20130524132612/@comment-6881629-20130524152340

That quest is radiant so it can happen more than three times (i know the wiki page only has three listed), i think as long as the people are alive and not already a Vampire you shouldn't have anything to worry about.

Try asking someone else for quests if your feed up of Vingalmo's quest but if your past killed Harkon and got all the special jewelry all the quests will be a bit repetitive. All the quests are listed here.