When is it time to change the windscreen wipers?

Is it still OK? - No Complaint

The formation of streaks during the wiping process is a good indicator for assessing how worn the wiper blade is. Ideally, there shouldn't be any streaks at all. Yet even if a maximum of three thin, persistent streaks form in the outer field of vision, or a maximum of one streak in the central field of vision, you can continue to use the wipers for a little longer with a clear conscience as replacing them isn't yet necessary.

Is it getting a bit critical now? - Please change the wipers

It's a different matter if thicker streaks form in the outer field of vision, or rather if a great number of temporary streaks are evenly distributed, even if these disappear again after a short while. Just like areas of water starting to linger on the windshield, these are a clear indication that the wipers are no longer functioning correctly and that they need to be replaced imminently.

The eleventh hour? Change immediately

Considerable veil formation, "chatter marks" and/or large areas of water which remain on the windshield are clear indications that the wiper blades need to be changed without delay. Continuing to drive in poor weather conditions poses a high safety risk under these circumstances due to the impeded view!