Recently I've been thinking a lot about writing in terms of iterated feedback cycles. Basically, the writing of a dissertation or thesis can be seen through the lens of the fundamental interaction between the writer and the committee, and especially the advisor/chair.
The committee chair is expected (required, really) to give the writer feedback and guidance in the move towards completion. It doesn't always work out so well. Even so, I recommend working under the assumption that what you want to do is to create a useful feedback loop.
This can be done by the simple expedient of turning work that is basically complete. I don't necessarily mean completely edited and proofread and formatted, nor do I even mean with all problems resolved and no questions of how to develop the material. I really mean complete in terms of the structure of the paper.
A structurally complete paper has an introduction and a conclusion. It dedicates space to defining the basic terms and premises. It presents an idea to be discussed and a purpose for discussing it.
Minor digression here: I often think about the basic five-paragraph essay that everyone (of my generation, at least) was taught to write in elementary school or junior high. There was an introduction, three body paragraphs and a conclusion. It's a structure that is pretty roundly dismissed, I think, by composition teachers now. But I think it's elegant, and provides a basic model for what all writing is trying to accomplish.
All writing--fiction, speech writing, essays, etc.--starts with something that is supposed to draw the reader in and orient them in some way. A writer of fiction tries to draw the reader in differently than does the speech writer or the essayist, but still the writer of fiction wishesthe reader to know what the book is about. (aside: for any who believe that "different/differently" must always be paired with "from", I disagree. As I write to be understood, and as I seriously doubt that the sentence is hard to understand, I pooh-pooh the scorn of any prescriptive grammarian who thinks it "wrong." I could continue this digression with references, but really...back to our main story.) "Call me Ishmael," opens Moby Dick, thus informing the reader that the whole book will somehow be about this person Ishmael. Fiction writers don't always want their reader to understand the full import of the orientation, but yet their words orient the reader, nonetheless. Brave New World opens with the sentence fragment: "A squat gray building of only thirty-four stories." The sentence orients the reader to the fundamental oppressive dystopian vision. (and a big raspberry to all the petty grammarians out there who are appalled by such casual use of language as Huxley's incomplete sentence.)
Similarly, all pieces of writing have some ending, something that wraps up the work and leaves the reader with some sense of what the work was about. In the case of expository writing, this tends to be some statement of what you have shown and the conclusions that you draw from it--the moral of the story, if you will.
And, of course, there's something in between the beginning and the end.
A complete piece will have all of these.
If, then, you submit a work that is structurally complete, your reader can read it and has to be able to explain why it's not complete, and thus give you feedback on the content and other aspects of the writing. If it is complete, you're begging to have your reader say "it's not complete."
I'm maybe going to say more about this later, but I got off on digressions and now have to run off...