Car covers don't last

I had a rain suit that had the rubber liner inside. I wore it the first rain of the season after 9 months of hanging on a hangar and the liner came off on my black work short like millions of snowflakes. It looked terrible and i didnt get all the flecks off for days. I think it rotted when I put it away not totally dry? My car cover is about as thick as a bedsheet, and gives about the same protection..:-(