I have voted on questions and answers then pondered on it to undo my vote the next day and it is locked in. It says I cannot change my vote until it is edited, but unfairly the people are not notified of Q&A edits that they have voted on. Can a feature be added to where one can be notified when a Q & A has been revised that they have voted on? or is there a way to extend the time period where one can change there vote? Why is it done this way anyways? Many times when I have a good question or answer I type it in right away not to forget it, but may take days or months to fine tune it the best I can or learn more about it down the road. If I try to re ask or answer it gets red flagged so I try to ask or answer Q & A perfectly right the first time but sometimes is impossible.
If you were able to change your vote on a post as much as you want, that allows some methods of gaming the reputation system, which is why it's not allowed. You get five minutes after you cast your vote to change it, and after that it's locked in unless the post is edited. So be careful with your votes. If you find yourself often wanting to change a vote the next day, you should probably just wait: instead of casting a vote, just make a note of the post you want to vote on, and then come back the next day and if you still feel that it deserves the vote, then you can cast it.
I should note that, if you have already voted on a post and you were going to edit it anyway, it's fine to change your vote after making the edit. However, your edit must materially improve the post, as with all edits. Making trivial or harmful edits just to be able to change your votes on posts (or for any other reason, really) is abuse of the system. Don't do that.