This kinda happens already, or at least it used to many years ago; you have to be an active user for your vote to count.
The most obvious effect is movies that drop in the rankings 30 days after release; people who just saw a movie give it 10/10 and then stop participating, so 30 days later they are no longer considered 'active' and their vote stops contributing to the overall ranking.
The most obvious effect is movies that drop in the rankings 30 days after release; people who just saw a movie give it 10/10 and then stop participating, so 30 days later they are no longer considered 'active' and their vote stops contributing to the overall ranking.