My vehicles windshields/glass was always going bad after being outside awhile. I have found that Paplio Clear Laminate sheets provide some protection for up to 3 years. I’ve had one car outside for a full year and it still looks okay. Not perfectly clear, but still looks like glass. I try to put it on when the vehicle is new and take it apart. Makes it easier to get on a curved surface that way. Just cut it oversize, peel and stick and buff some. I use it on signs I’ve printed on the Paplio Ink Jet Vinyl and it helps them last a couple of years. I know others have this problem, if you leave them out as I do.
http://www.papilio.com/other%20poly%20focus%20glossy%20over%20laminate.html