IMO, this should be in the faq's. I find the system as it is moderately confusing.
Having downvoted a Question or an Answer, I believe I can reverse my downvote by clicking the downvote button again, provided it's been less than 5 minutes. Is that correct? After 5 minutes, I can't change my vote, no matter what, until after the Question or Answer has been changed. Right?
Every time I get myself in this position, it always seems natural to click the upvote button, but as far as I can tell, clicking the upvote button in this situation changes my -1 to +1, a change of +2, and also immediately freezes my vote as +1, so I can't fix my mistake. Very Frustrating.
Are the mechanics for reversing an upvote the same?
I don't downvote much, and I never downvote, as far as I remember, unless I can see a way to explain why. Precisely because I go to the trouble to explain, not infrequently I realize that the Question or Answer is not so bad, and I want to change my mind, but I find the mechanism for changing downvotes very unUseful.
I guess this is a feature-request if I ask for the upvote button and downvote buttons to go between -1,0,+1 by addition instead of as currently. For example, clicking upvote successively would cause the transitions $-1\mapsto 0\mapsto +1\mapsto +1\mapsto +1...$ (without time limitation, the reason for which I do not understand). However, this is a change to a fairly low-level aspect of the user interface, which I presume will not be implemented without better reason than I've given here.
EDIT: I (the questioner) have voted to close this Question. I see a very similar one that the search didn't find was only just asked and closed because something like this is off-topic here and should have been put on the main meta site. I come to meta too rarely to be able to use it effectively.