Maybe this is addressed up above, but I just had an agent proactively combine three FFCs into a single FFC. Since I don't think you can apply more than one FFC to a new flight (still true, correct, unlike ETCs?), this helped me by avoiding having two small FFCs plus one larger one. None of the original FFCs covered the entire cost of the flight I wanted to book, but the new combined one did. When I used the new combined FFC, the residual credit came back as a new FFC (the wiki still says it comes back as an ETC, but that hasn't been my experience for months).