How often do you have to clean and/or replace your plates for a HHO dry cell?
I have never cleaned mu plates, but I have always used NaOH (caustic soda) and pure distilled water. Oh, I once tested windshield antifreeze and NaOH, at minus 21°C and it only ever-so-slightly discolored my system, but worked beautifully!. But I never had to clean them at all.
If you are running distilled water and either KOH or NaOH as a catalyst, you should not have to clean your plates.