Here’s some things to note about your car’s plastic convertible windows:

• If there’s too much oxidation on the window, you can use commercial cleaners or plastic restorers to bring it back to it’s original condition. You can also use protectants and conditioners to give added protection to the window from the sun and rain.
• When the top is folded, check for some snags or creases on the top and on the windows. Try to smoothen them as much as possible as these may result to tearing later.
• Use soft cloth when cleaning the windows. This is to avoid scratches and damage on the surface.
• For tears, there are fabric kits available in the market. This can patch-up the tears without the repair attempt showing off too much.

Image from:

http://lib.store.yahoo.net/lib/classic-motoring/ConvTop3.jpg