For reasons lost in time I always use page-break-after, and I know it works. The Woman in White by Wilkie Collins in the MR Library has a quite idiosyncratic structure, and I've used internal page-break-after to start new pages without needing new files.
If you put a page-break-after within a single file most ePub readers that I've tried will just use one of the other (the CSS or the file ending) to make a new page and have the next file follow on immediately. Apple iBooks in their ineffable wisdom will put a blank page between the two files if you have a CSS page-break, so I suggest that you don't end an html file with a CSS page break if you want it to work in iBooks.
I don't know of any desktop ePub reader which honours pagination. Only the stand alone ePub reading devices do.