How often do you need to replace your masks? Far less often than most people think.
This web page (not peer-reviewed, but probably still good) (2019-11-11) reports that you can reuse your mask many times with minimal degradation, even if the air is really really gunky.
This paper by the inventor of the N95 mask material says “masks will retain 92.4% FE after boiling” (presumably compared to 95% filtration before). NB: It does say to not boil the elastic straps!
This Twitter/X thread author tried boiling heavily-used masks and found that their filtering effectiveness dropped from a bit more than 98% to a bit more than 97%.
This unroll of a Twitter/X thread describes how the author swam in their mask with even less effect. The swimmer did before/after testing, both when it was wet and when it was dry. Their 3M Aura 1870+ (which coincidentally I now have 440 of!) dropped from 99.0% effective to 98.2% effective when soaking wet!