picture this...the underside of your deck (after mowing) is clean except for a few 'corners'. Since these grassy corners were created by the airflow of the spinning blades is it really necessary to remove this grass? Think about it, the deck, we'll say, started out clean. After hours all that's under the deck is this small amount of grass in these 'corners'. The mowing process obviously accumulated this amount of debris but also limited it to this amount of debris. [I am talking about a Turbo Force deck (and many other commercial decks), I am NOT referring to a home-ownet 20" push mower that completely cakes up with grass on the entire underside of the deck] I would think that you still have proper aerodynamics as you just did hours of satisfactory mowing. What do you think?...is it necessary to remove these small accumulations of grass each time??