The humidity issues on a boat vary with climate which depends on geography. In the PNW, the worst period is September-November. Cliff Mass explains why.
http://cliffmass.blogspot.ca/2017/03...driest-on.html
On a warm humid day the humidity might be 75% at 20 degrees C. If the temperature drops to 15 C overnight in the inside spaces in your boat, the humidity goes to 101%, so condensation occurs. This is a useful calculator.
http://www.richard-stanton.com/humidity-calculator/
This time of year, it's useful to have some heat to raise the inside temperature a few degrees. The dehumidifier will not work properly below about 8 C, so you are better off raising the temperature by a few degrees, lowering the humidity in the process.
The bottom line for me is to ensure a good dehumidifier is on the boat from September to December and it helps when cooler to raise the temperature on the boat a few degrees. It's less necessary for the rest of the winter, unless a tropical system passes through.