I got these replacement filters shortly after I bought the aspirator. I found that you wouldn't need that many filters after all. I have been using the same filter over and over again. Most of the time it doesn't get soiled. In case it does get soiled with mucus, I just rinse it under water, squeeze it and let it air dry so I can use it again next time. So this box will probably last as long as I need to use the aspirator.