100% always. Lose my mind otherwise.
I don't even want help in the kitchen from someone who isn't cleaning as they go. I end up cleaning up after them and it would be faster if they weren't there.
"The best way to help mommy," as they say, "is to stay out of her way.
Edited to add: cleaning as you go can end when you've plated the food, assuming you're eating with everyone else (and not diving into making the next course). There's no point in letting the sauce congeal on the plates as everything gets cold because you're obsessively scrubbing the last pan of the evening.