First of all I think oryx was always a male. They were referred to as sisters but also never referred to as princesses while on fundament. I know for a fact they were called princes at one point. Second, their "10 year" life cycle is NOT and SHOULD NOT be thought of as earth years, for all we know those 10 years could have been 100 but I digress. Third, their voyage to the worms took them almost all their lifetime so it's very unclear how much time they actually spent looking for power. It's awesome read though.