As mentioned above, there are no hard and fast rules. Given how varied character powers are and how different people react to different scares, there's no specific time requirements. Tiny scares can stack up, but it's going to take a lot more little scares to be able to perform more impressive feats of magic than one big scare. Please use your discretion. We will not be policing this closely unless it becomes necessary. If your character is only ever performing low level scares, it will take them a very long time to fully charge or they may never achieve a full charge.