In my over 25 years of owning 4 convertibles, I have never once put anything on the top except water to clean it off. If however this is a daily driver, it wouldn't hurt to put something on it. My cars are only driven in nice weather, never see rain, snow, or any type of weather but sun.
2012 1SS Triple Black Convertible
"The Assassin" 8/4/11 - 4/17/12
2012 1SS Crystal Red Convertible
"Cherry Bomb" 4/17/12 - Lifetime?