As another commenter noted, it depends on your air, but a decent HEPA filter (H13/H14 etc.) will last a very long time if you remove the coarse dust first with

As another commenter noted, it depends on your air, but a decent HEPA filter (H13/H14 etc.) will last a very long time if you remove the coarse dust first with a prefilter. The prefilter is typically a lot cheaper and is replaced more often. Even some non-woven filter fabric (like that used in vacuum cleaner filters) will dramatically increase the HEPA filter life, is super cheap, and can be washed for reuse. My purifiers use an F8 prefilter and H13 HEPA filter, and the HEPA filter will last about 2 years. Filter class info here: https://www.emw.de/en/filter-campus/filter-classes.html https://www.emw.de/en/filter-campus/filter-classes.html