Before installing new wiper blades, I saturate them with Aerospace 303 and let them set, preferably 24 hours, but at least overnight before installing them. I believe it extends the life of wiper blades, and helps keeping them working flawlessly.
But I'm also a huge supporter of using OEM blades. I use Subaru blades on my wife's Outback. I replace them every 12 months, but they could go much, much longer, as they are always still performing with no streaks, stutter, rot, or any other issue.
The E350 gets Bosch Aerotwin, which appear to be identical to the Mercedes blades, except they are missing the tristar on the end cap, and instead have the Bosch brand. These also perform very well, only being replaced because I'm a PM schedule kind of guy. No rot or deterioration at all when I replace them.
I'm also a fan of glass treatment. A good windshield treatment will minimize wiper blade use/wear. This works for me, because I find wiper blades running across my windshield to be annoying.