If one uses a hooded NM aperture, I most strongly recommend using one of the plastic rear sight covers to protect the hood at ALL times when you are not shooting the rifle.
ALSO and this is highly important that some folks do not think about. When you get done shooting with a Hooded aperture, RUN the elevation pinion all the way back down while counting your clicks and write down the number of clicks you used. Then LEAVE it down until the next time you shoot. If you leave the Hooded aperture up and turn the rifle upside down on a bench, you can snap the hood right off the aperture.