He doesn't re-quote the lines. It's just that he sometimes discusses the excerpts in the text below the epigraph. The convention generally is that epigraphs merely ornament the book, and are not strictly 'part' of it. So if the quotation is subsequently discussed '('In these lines Proust reminds us that lying in bed all day ...) the discussion is violating the proper role of an epigraph and behaving as if it were a standard extract.