For two people living permanently on am SM2K, we find in cool climates you need the following to avoid damage from condensation arising from high humidity.
1. Always run the kitchen exhaust fan while using propane.
2. Run at least two dehumidifiers permanently. We have the Eva-Dry EDV-2200 with peltier technology, which is a bit of a joke and is not sufficient if people are living on the boat. Don't recommend it. We also have the DeLonghi DNC 65 with desiccant technology, highly recommended for low power use averaging about 50W, low noise, small size, and ability to keep dehumidifying even at low ambient temps when we are out and about. Runs in the U.S. if you run it from your 50Hz inverter.
3. Run the Eberspächer diesel heater at least once a day and for at least one hour.
4. On any days with low ambient humidity, open all hatches and run fans.
5. Install humidity monitors throughout the boat, and especially in the problem area on the berth above the batteries. About $40 total.
6. Open cabinet doors and rotate stored clothes as needed.
En route, Thermopylae to Skiathos