How often do yall replace pellets?

I usually replace Mambo's pellets when she's eviscerated about 90% of her pellets and it's just dust. Is that wasteful? Am I being hasty with it, or would she actually eat the dust if I left it? I don't have a photo, but it's usually something like 1/3 of the food bowl being pellet powder.

I haven't experimented because the last thing I want to do is force her to go hungry for the sake of finding out my answer.

What do you you all do? How often do you refill their food bowls?