ICRT allow teaching Reiki I&II over 2 consecutive days or with a gap in between each level because this is how Hayashi Sensei (one of the respected founders), taught Reiki. When he was teaching at his school he taught them separately, but when he was traveling and teaching he taught Reiki I&II together in five days with about three hours of class time each day.  If you are a new teacher ICRT suggest you teach them separately, but as you gain experience you can decide if you want to continue to teach them separately or if you’d like to teach them together. This is an individual decision.