19 GHOSTS books and minor characters

Jon F has a GHOSTS question, edited slightly to remove spoilers:

“I think of the Ghosts and Ghost Exile as a rather large set of books to read, and so, I have a question: During your time as an author, and especially for the Ghosts and Ghost Exile series, did you remember the minor characters well enough to include them in the later books, or did you sometimes have to go back to previous books to add them to the protagonist’s recollections?”

Yes. 19 books (and I’m starting #20 in a few days) is rather a large set of books to read.