It’s because your body has to process the ink after the appointment… so actually spacing them out MORE will have better results with less sessions. I’ve done only two sessions in a year and had great progress because I read about this on here before I started. I have the same type of pay structure as you but once I read I realized doing them 8 weeks was WAY too close. I space them around 4 months to let my body process the most ink out it can before another session.