First of all, keep your Dampp-chaser plugged in. If the humidifier goes dry, the Smart Heater Bar will be shut off by the humidistat and warning lights will flash until water is added - but the dehumidifier will still be available as needed.
We keep the system clean, change the humidifier pads, and supply a fresh bottle of additive (normal use goes through one bottle per year). We charge $60 for this service when at the piano to tune and $120 if we need to make a dedicated visit.
*Even if your piano does not require tuning in a given year, a Dampp-chaser service protects your instrument and keeps it in better tune!