Air good
Yep got em in my flat too.
We seem to go 71/2 -8 months on jus the ceiling fans. Then occasional a/c use and then 2 months pretty serious a/c use. Our split a/c s have upgraded filters in them and they need regular cleaning so they might be doing something as well.
Whether the a/c pumps it in, or it drifts in through the window, with an air purifier in the kids room at night we hoped that the air was a little better ! Anything is better than nothing. If the state of the filters was anything to go by they were working !
Cheers
FG