How often will I have to replace filters, and how expensive are they?

Most app-connected purifiers track filter life and notify you in the app. Across the reviewers we read, real-world filter life lands in the 6–12 month range for Levoit and Winix HEPA filters at moderate use, and Dyson's marketed multi-year filter claims drew skepticism on r/dyson where users report earlier replacement under heavy use. Budget roughly $30–$80 per replacement for mainstream brands and significantly more for Dyson.