I think that's a function of the quiz engine plugin - once a quiz is over, it's pretty much gone from view.
Don't worry about duplicating any previous ones. There are enough people that haven't taken quizzes that it'll be ok to dupe a few.
Generally, a quiz author will set a % correct level on the quiz and award something (REP or likes) for any one who takes the quiz and gets that score or higher. Totally up to you on how you want your quizzes to work.
Have some fun with it!
Bookmarks