I gotta say that this workflow is both young and sort of an improvisation. I only got a Kindle a few weeks ago and I gotta say that when you know nothing about coding and ebooks, it's all very overwhelming - I took cues from whichever website or forum thread I happened to land on, leading to quite a circumvoluted method made from bits and pieces.
My forum peregrinations only lead me to discover Sigil a couple of days ago, so I still have much learning to do
I however quickly realized that I'm somewhat of a control freak when it comes to my ebooks, and I can't stand finding a stray tag that I didn't put myself, or being unable to check exactly what it does in the css or to tweak the quotes' bottom margin whenever I feel it's 1pt too wide.
I also might have gone overboard with my "formatting options". I have set classes for every type of situation: books with Parts and Chapters, Parts that have specific quotes, Chapters that have introductions, Subchapters that need a page-break-before, etc. - all of those having different text sizes, indents or margins - depending on the book, of course.
Also I might need to mention that most of my ebook-making has to do with free content: public domain books, fanfic, essays, etc. that are published on websites and that often need
a lot of precise formatting to be readable.
But you guys really made me wanna look at the whole process from a fresh perspective so I'll give Sigil another try, and try to let go of the formatting OCDs.