I agree with Alex - I wouldn't have put much effort into it either, considering it wasn't being graded.
I'll confess I'm a major procrastinator myself. I think many of us are whether we want to admit it or not. As long as a job gets done well and is completed on time, that's what really matters. For me, it's not that I'm unaware an assignment is due until the last minute, it's that I know it won't require much effort on my part.
I wouldn't go as far as to say it's the best habit though. If you think about it - many who start assignments early may put in about the same amount of time on work as procrastinators. The only difference is that an early bird would have it done right away, and enjoy their free time afterwards. The procrastinator would enjoy their free time early, and have it done later.
So the working styles may not be so different in those regards. However, if a procrastinator is not achieving their highest potential on their assignments, then there could be a problem. A student who can judge their abilities well and plan accordingly (whether early bird or procrastinator) is sufficiently disciplined in my opinion.
Are there less procrastinators in grad school? Probably. Some assignments are equivalent to writing books at that point (depending on area of study) and it's better to complete the work with plenty of time to spare than risk being rushed and losing points on quality. It takes time to learn, but being a quick starter makes more sense in circumstances where a high level of quality is important. It's something I'm working on myself.
I do see what you're saying though, Kim. If that's what works for you, no problem. I'm the same way, I tend to spend a lot of time thinking and little time actually writing. Still, you have to admit - it depends on what you're writing. If you're quoting heavily and have a huge bibliography, there's usually a bit of reading and planning ahead of time to be sure that the references are appropriate. Spontaneity in the writing of the paper itself is fine, though. If you're trying to publish a novel - it usually makes sense to get feedback and then go back and edit some of the original material. If you're trying to convince me that all writing should be done instantaneously, I'm going to have to disagree. There's a huge difference between doing what's required to achieve good grades and competing amongst others in your field with quality in mind.