Originally Posted by xmlgirl
Are there any guidelines concerning when and how you should break the HTML document up? ... Just wondering if it is worth the extra effort.
Strictly speaking, there is no need to break up the HTML file(s) in an ePub during the editing phase
. As others have already said though, there are practical concerns to consider when you produce the final version for distribution.
There can be advantages to having a single file while you are editing. At the same time you may find breaking the book into multiple files also has some advantages while editing. In particular, if you are using Sigil as an ePub editor you will find that it can be a bit sluggish when rendering in the preview mode when the HTML file is very large. In Sigil, the Search&Replace function will work across multiple HTML files eliminating one of the main issues with editing multiple files.
On the other hand, if you are editing the HTML with other tools, you may well find that having a single file is advantageous. Just be sure that the final published version is split as necessary to avoid issues with ADE, the dominant reader engine.