When a shaman is teaching a character a spirit magic spell, can he do something else? Or is he/she committed to working with that character all week, 6 to 8 hours a day?
If your clan only has one shaman with the teach spirit magic spell, and it takes a week, I'm assuming that they can only teach one spell at a time. Or can a shaman work with 3 or 4 characters at the same time during that week teaching each a different spell?
My players will have some 7 or so weeks of down time and will want to learn some spells from their shaman and cult leaders.