Question about Xiaomi Mi Air Purifier Filter

There are copies made in Asia, but I recommend the original. That said, you can continue to use the same filter for a long time because its real life in a lightly polluted atmosphere is much longer than that calculated by the application (it's not a 'wear' detector but a calculator of the number of hours based on what the airborne particle detector measures. )
And also buy one in advance ...

I always use this one. So cheap and it does what it has to! (I always buy 2)
As emile writes below, the filter lasts a very long time for us. Don't go to the app because it gives you a calculated value/duration.