Master Documents, such an underutilized part of OpenOffice.org is actually very useful tool when you have to write documents more than few pages.
Master Document is basically special version of OpenOffice.org Writer window that let you combine multiple documents to make one document. It is very nice as you could be editing chunk of each file, then combine them into one large document.
This approach is especially useful when you create documents containing a lot of graphics. Having a lot of graphic can consume quite a bit of memory, and you may find it slow to edit the file. This wouldn’t be too much of problem if you are just editing few pages, but it is when you edit hundreds of pages.
Other benefit of this is that you don’t have to worry about formatting when you are writing. You can apply formatting globally after you have done writing. This way, you can focus on contents, and then you can have consistent formatting of the document when you are ready to create a final document.