Its really up to you when you do the pulls. You can pull 1 by why or do a ten pull whenever you obtain enough to do so. You just have to keep track of how many you've put into the treasure. The only thing that resets is the free pull timer, not the counter or amount of scrolls you've put into it. You wouldn't have to for example, dump all 900 scrolls at once for a Susanoo Sasuke. Over the course of time you'll eventually pull super rares, it just takes an extremely long time if you aren't pushing up the counter. 10 pulls are preferable as you get a guaranteed 3 star. Even if you already have them its better to collect frags.