I often hear from people interested in my services: "I have only four weeks to complete my dissertation" is their cry. This is possible. But it ain't easy.
When you're writing something as large as a dissertation, there are just too many logistics to handle. Large papers don't get written quickly--at least not by most of us.
More importantly, large papers don't get approved quickly: someone has to read them. So, if you only have a few weeks left on your dissertation, the first thing you have to do is make sure that your faculty committee is on board, and willing to do the last-minute reading that you need them to do in order to finish.
Because your dissertation has to be approved by a faculty committee--usually three, or more, professors--you have to plan for weeks of time to circulate it and get feedback.
When you have a year to work with, or six months, that's plenty of space in which to handle the timing requirements. But if you're down to six weeks, and your dissertation is long, that feedback time is a huge proportion of the time you have left.
You can swing it with a committee that is going to do the reading, with a committee that is ready to take on that project. But you have to make sure they're OK with that process, because it's a big commitment in the lives of people who are very busy. It's not that they don't want to help; it's not, even, that they wouldn't rather work on your dissertation than many of the things they're committed to. But they have committee meetings, administrative responsibilities, classes to teach, other students with dissertations and oral exams, not to mention their own research. So you have to be able to work with them, because they've got plenty of other pressing engagements that are no less necessary than your dissertation.
One thing that can really help with this kind of situation is to plan ahead: if they know what's coming, then there's a much better chance that they'll be able to make the time for you.
A similar issue is involved in working with an editor: turnaround time is going to be non-zero. A few days, at the least, are needed for long works. When time is short, this kind of assistance can take up a large proportion of remaining time.
The more you can plan ahead, the easier it is to manage the remaining time.
Mostly I've focused on people with approaching deadlines, and what they can do and what they should expect. But better still, than having a good plan for what to do with a short deadline, is planning ahead enough in advance that you're not frantically trying to meet a deadline, but instead you start thinking about the process of finishing up a dissertation ahead of time.
I know this is easier said than done. I know that, if you've been working on a project for a long time, you're ready to be done with it. I know that it costs a lot of money to enroll for another session while still working on the dissertation. If you have an approaching deadline, you have to plan correctly, and part of that is getting your committee ready. Another part of planning well, is to make realistic assessments and then work on plans that match those assessments. Many people get themselves in trouble by making very ambitious plans without any good backup, and then they compound the problem by letting their disappointment at their failure interfere with their progress towards their goal.
So plan ahead now. Whether you're planning or hoping to finish in May or December, or May 2009, your plans should include the time it takes to get feedback--sometimes more than once--the feedback process can take a month or more.