I'm a lodging refugee so I haven't touched the system yet, but

I just found out that if a Heart is S rank on the Heart Exchange screen, it shows (Important). I looked it up and the hearts you can exchange depend on your main story progress and are then randomized. I plan to touch the lodging system within this month… My GPS is too fickle, it reaches rivers stably now, but lodging is only rarely reachable from home. I really don't want to exchange for Alacrator… but I do want the Plasoul, so I guess I need to collect more from other Chapter 18 deliveries.