I have a 2012 Cameo which is a 4 season 5er. I also researched the windows and while the double pane will add some insulation, my search and advise was not to get them because of the two following reasons:
They can crack.
RV's with the double pane might have to replace them on a 7 year cycle due to problems.
They also add weight. I have the Heir frameless windows and have had no problem with them. Should you get condensation, which is likely on the inside crack open a window or vent to relieve your unit of the excess moisture. This is what I have been told. I have not had this problem yet, and have not used it in the Winter to find out.