A more thoroughly thought-out (easy to implement) architecture would be for voting to be disabled on all threads after x days, with vote tallies being displayed

A more thoroughly thought-out (easy to implement) architecture would be for voting to be disabled on all threads after x days, with vote tallies being displayed at that point. If you guys want to fancy it up, you could implement the feature where users could indicate they're done voting on the thread and see the tallies early, and you'd only have to keep track of x days worth of user thread status flags before you can purge the data.