I used to do it your way. But I wanted to count books read in a period. A boxed set/Omnibus is 1 'book' (line in Calibre), So I now EPUBSplit (and mark the omnibus with the
flag date 1999, meaning it has been fully split (I think I have 1 boxed set with 13 volumes, not all have been processed. It was $3

)