I install a new blade ( insert ), purchased from the dealer, in the spring & in the fall.
A real good cleaning of the windshield every other week yields great results.
Can't believe how much oil, grease & garbage accumulates in a span of two weeks.
Also, if you happen to use a combination wash/wax solution for cleaning the car, it tends to leave unwanted residue ( wax ) on the windows.

__________________
2007 C 230 Sport.