The culminating requirement of the Ph.D. program is the dissertation. The dissertation is evaluated by a Dissertation Committee which is usually, but not necessarily, the same committee that conducted the Preliminary Exam. As with the Preliminary Exam, a Minor Area Representative is required. Any committee changes should be registered with the DGSA as soon as possible.
The dissertation can be of any style that is acceptable to the committee, including "book style" and "article style." These days, most dissertations are "article style," and comprise two to three standalone papers of 8,000 - 12,000 words each. Typically, students can (and should) use published or accepted single-authored papers as part of their dissertation. 
The dissertation should be defended by the deadline set by the Graduate School. Because of Graduate School requirements, we can only guarantee students funding for the first 5 years but in practice we always fund students in good standing for 6 years if they need the extra year. Only in extraordinary circumstances is it possible to receive funding for a 7th year. See Financial Support for more information.