Lets not leave the Service people out, they want to get a bonus this year, too.

So make the sponge replaceable, but only with a field maintenance call-out. The sponge unit will have an NFC chip in it that if it's removed will lock the unit out until a Technician access code is entered to restore the unit.

We can sell it as a whole periodic maintenance thing - give the service guy a can of air-duster and a roll of paper towel to wipe the thing off.

(I feel dirty even writing this because I'm sure someone is taking notes and thinking these are great ideas)