Depends where you live. I bought the vehicle in Florida and never needed to change the blades.
Then I moved to Colorado and Wyoming and I had to change them every 4 to 6 months depending on how much ice they saw.
Here in sunny California I haven’t had to change them in over a year.
Where are you live, what type of conditions they see, what temperatures they see, and how you use them and where you drive is going to affect they are lifespan.
I will say, the worst thing you can do to them is start them up if they are frozen to the windshield.