my car is a 57 plate and on its second set of blades, I'm getting a void smack in front of the driver! but it only happens in the worst heavy rain imaginable! which is all the time at the mo! beyond that they are fine...
how long should wipers last, I'm convinced things aren't made like they used to be, I only had to replace blades once on my 156 which was after 6yrs or so of the car's life.
my old rover 414 needed blades more than 12yrs after leaving the factory...
I had a similar problem - until today. A large, triangular area from the pillar extending well into my eyeline. It remained unswept after replacing blades and many attempts at bending the blade. I was even convinced that the new screen was warped but had put off calling in at Autoglass just through lack of time.
However, I did a search in the 159/Brera lounge and found a useful thread by 427scr called "Bera eating its wipers". It sounds like a fairly common problem manifested by the unswept area and the wiper arm catching the leading edge of the bonnet at the top of its arc. I had heard of the latter quite a lot but hadn't made any connection to wear in the mechanism.
427scr has helpfully posted a guide and some pics. It is an easy fix, you need a couple of Torx screwdrivers, a 10 & 13mm socket, 3 off large M6 washers and some copper slip. It is a really easy fix, less than two hours. - I struggled getting the multi connector off the wiper motor for ages until I realised there's a little clip you have to press with a screwdriver and...presto!
Do a search, I posted a thanks note earlier.
As to how long blades should last, I think the official manufacturers' line is they should be changed annually but you can get longer depending on the usage, especially in icy start ups which can be a killer. Basically, if they are smearing, squealing or look ripped you need to change them.