I've switched all my vehicles to Silblades after running them on the Porsche for 6 years without needing to change them. They are still perfect.
I'm running conventional blades hey do make a 13" beam type blade:
http://www.silblade.com/Flex-Blade_c_8.html
The silicone wipers don't break down from ozone like rubber ones. The way it works here in SoCal is: Put on new wiper blades... 6 months later you get some rain and it just smears the water around because the rubber is toast...