Nordic Pure now offers the replacement Hepa filter for the SPX Series Lightning Air Plus. The life of the hepa filter depends on the environment it is in. If it is in a heavily polluted environment, for example a residential smoking environment, you would probably want to change the filter 3 to 4 times a year. If it is a commercial smoking environment, you would want to change it more often. If it is not in a heavily polluted environment, you may get 6 months to a year from each filter. We recommend vacuming the back of the filter every month to extend the life.