I bought a second hand car 18+ months ago and there was no information on how recently the wiper blades had been replaced. This wasn't an problem as the blades weren't obviously worn and they did their job perfectly adequately. The back wiper did squeak, but as I don't use it that often it wasn't a problem.
However, this autumn I became increasingly aware that the wipers weren't clearing the water very well - they were smearing the water across the windscreen rather than moving it away. I have replaced the blades as they were clearly failing, but I was wondering how long I could expect these replacement blades to last.
I am in the UK, which, while it doesn't have extremes of weather, does often get to experience all four seasons in a single day ;). Other countries/continents will have different wiper blade life expectancy of course.
I've done a Google search, but all the sites I could find seem to be sponsored by motor manufacturers or retailers/repair shops who have a vested interest in getting you to buy new wipers every year (or every 6 months in one case). However, I don't think that this is realistic.