After buying quality glasses, we recommend to carry them in protective case. It protects them from unwanted environmental influences and scratches. This is  unpleasant mostly for mirror glasses, that are more susceptible to scratches. Avoid sea water. It can dissolve the mirror film. We do not recommend leaving them in the car during summer days. High temperature can cause deformation of the plastic frame. Do not wear them as a headband - it cause loosening the screws and bending the ear pieces.