Personally I like getting a build up early then continue to work on it until the deadline. That way if I have a build failure on the last day and can't submit the latest build, at least something is submitted. Plus, it's easier to have people play test a build this way. Also, I wasn't sure how much time I'd have the rest of the week, so I got the core gameplay loop and levels in. After that I have just been making small changes since then