If I know how to answer the question, I start writing--and usually I'm not satisfied until editing the answer multiple times. (I write answers the same way I write essays and papers.) Generally, should one just keep editing the saved draft instead of publishing that answer?
A couple other things worth mentioning:
The volume isn't as heavy here as on StackOverflow. There are few cases where you benefit from posting early.
The length of answers shouldn't be so long that editing is a big deal. If you get to the main point quickly and cite some references, then that's all there should be to a good answer. Beyond that, your post might be straying into original-work territory.
I think that most users read a new answer more carefully than an edited answer. So, if you edit your answer extensively after posting it, your post may not reach the score it could get if you would have posted a polished version later. This is not only bad for your reputation, it also means that your post is read less because it's further down the page. In addition to that, the asker gets a notification when you post the answer, but not when you edit it.
Minor edits are fine and encouraged, but if they make the difference between an OK answer and a good answer, you should wait with posting. Notes in an answer like "This is unfinished" are a "not an answer"-flag indicator for me; after all, you never know if the post will ever be finished.