I ask because I set up a plan to get as many supports in a single playthrough as possible and they seemed to get messed up after chapter 17. As it is right now, I've kinda afraid I missed out on Ike/Titania A because I'm on the penultimate mission and I think I used up my two titania-free missions already. So if I sent Titania in as a reinforcement, and that makes her not count with Ike for that chapter, for instance, It messes it up.