Like Earth Golem said, Foxy loves attention, which means that the more you keep cams on her, the more it delays her.
Try not to use cams too much, especially for the other girls, because they will not be your priority unlike Foxy and Freddy. If you can stall your power until a little after 5 am, even if you run out of power, you have a high chance of clutching and finishing the night before Freddy can jumpscare you from the left door (which is what she does after you run out of power).