If you have, say, 30 chapters in a FrameMaker book, you can
update the content in RoboHelp by each chapter. That is, you don't
need to update the whole book when you want to update the chapter.
Use "Update" for one document and "Update All" for all FrameMaker
documents/books in RoboHelp project. However, you cannot Update by
HTML topic in RoboHelp. For example, if a chapter in FrameMaker is
converted to 15 topics in RoboHelp, you need to update the whole
chapter.
There is another powerful feature in RoboHelp which helps you
preserve the topics in RoboHelp from any update. Right click on the
FrameMaker document (chapter in a book) and select properties. In
one of the tabs, you can select topics which you don't want to get
updated when you update the Chapter. This feature is powerful
however should be used with caution.
I hope this helps