Combing farm units with 1 unit 3 plat spirits is absolutely unsustainable. You should be doing 2 and 2 at most, and I even still have to mix in some 1 and 3 or using junk fairies (golds I no longer need and bronzes from stamp card and occasional events). That's running Phalanx 2 on weekends and Wednesdays and Spirit Rescue G both Tuesday and Friday, which has an even higher return on plat spirits per stamina spent. Unless maybe you only use tin cans on non-plat units...