Your pet's abdomen should remain thick (not skinny). If it gets too fat, you can take a break. If it gets too thin, it's time to feed it! 0 to 7 insects per week is good, depending on your pet's size. They can go several weeks without food or eat 7 insects, one after the other.
A mantis is like a bottomless pit. They will often eat well past the point of necessity.