Of the three mezuzah cases here, one mezuzah was posel. This is a common occurrence. If a good new mezuzah costs $85 for arguments sake, five new outdoor cases costs only $40! So in order to protect your investment, and to protect the kedusah of the mezuzah, and Heshem’s name which appears in each mezuzah ten times in the two parshios of Shema and V’Hiya, and one time on the back of the mezuzah, update your cases when they look weathered.