If you have published more than 4-6 systematic "long" papers during your Ph.D., and each paper has no overlapping content, then the doctoral thesis should be very simple. When writing a doctoral thesis, you only need to contact your work during your doctoral period. Usually the first chapter is the research background, and this doctor finished writing the topic in the first year. But the deeper part is the research content of 4-6 chapters, and it is enough to slightly expand the published papers (the tutor of small papers has changed). Come down again, this is the conclusion. It should be solved in two hours. So, one month should be enough.