I use my Trawler all year long and actually prefer cruising in the Winter (no crowds). The boat is very well insulated for noise reduction, but that has the side benefit of also working to retain heat.
The windows are not double pane, but are very thick Diamond Sea Glaze that do not have condensation issues. I could put the Plexiglass Blast Shields over the large Saloon Windows for additional insulation, but have never felt the need (except when transiting the West Coast).
I think the key to spending the winter on a trawler is adequate and redundant heat sources and running a dehumidifier on the boat occasionally. I find that works best to dry towels and showers in our wet, cold winters.
Scott (Boydski) Boyd
Yes Please, Grand Banks Eastbay
Sea Eagle, Nordhavn 47 (sold)