How long can you change your vote?
I just received an 'unupvote' for the above answer. My understanding (from experience) is that once you have upvoted, you cannot remove said upvote after a certain amount of time has passed, unless the post has been edited.
The answer was posted in September last year, and hasn't been edited.
Who (apart from devs) has the power to do this? Or is this something available to everyone and I've just not worked out how to do it yet?