Got my rocker covers replaced yesterday. They appear to be a hair longer so maybe they will not shink and crack next winter, if it is the cold doing it. All covered under warranty and didn't cost anything other than my time. They are held on with 4 plastic rivets at the ends, plastic clips along the top end and 2 sided foam tape along the bottom edge. Noticed that the rockers them selfs are pumpped full of spray foam. How long till the hold moisture and starts to rust?