Yes to the eRapid for saline.. Sometimes to the Aerobika - many days I don't need it - the saline and a quick walk bring everything up easily for me. I sterilize on Saturday - so after 4-5 uses (I soak and rinse every time.)
Here is what Pari has to say about the handset, "Replace after 3 to 6 months (see also information from the previous question). Please note: If nebulisation time more than doubles, even after using the easycare cleaning aid, the aerosol head needs to be replaced."
https://www.pari.com/int/products/eflow-rapid-inhalation-system/frequently-asked-questions/