only issue i have with the original blades is the spring pressure points, 6 in all on each blade, as the wipers wear these pressure points scratch or wear the screen unevenly eventually giving 6 wear lines. Its fair comment that you/ we should change them before they get that worn.
However with the flat or aero style blades, it doesnt bother the screen if they are left too long as the pressure is even accross their width due to the design.
They are less suited to the omega screen due to its curved shape, esp rear estate screens. You will notice the modern front screens are considerably flatter, and for that reason i spent a fair bit on Bosch aero twin bades as recomended by a member on here, they work beutifully, and hug the area by the tax disc a fraction better than the originals which still lift in that area,not that matters a jot.
I had valeo before and the bosch are better due to the second blade behind the tip and they seem a little softer rubber making them smoother.
I also noticed that it helps their operation considerably if they do not catch on the spring on the underside of the wiper arm!