I feed mine very day, or as often as he feels like eating, which is actuallyl sometimes more than once a day.
Can you afford to feed it every day? Then why not do so? If the carcases are affecting your water parameters you may want to feed less, but I can't see any other reason why your mantis should be dieting (so to speak).
I love watching mine feed, so I feed it a lot.
JJ.