No issues or problems with it affecting the window? Was it stick on or the stuff you mist the surface and squeegee as that's what I am thinking of using.
I used the film that requires water to adhere it to the surface. It was a bathroom window, so not that large. Firstly I washed the window just using plain demin water and a soft cloth to ensure any grit was removed. Then used Vuplex acrylic cleaner and let it then dry thoroughly. Unlike where I have "filmed" car windows I could not go up to the edges of the caravan window because of the profile curvature, so I had to cut a section of film to just cover the flat area, which actually wasn't that flat. Even so the first attempt did not go too well as even with the window shut it had some flexibility compared to a glass car window, and the film buckled. Second attempt was better and it went on satisfactorily, as I used less pressure on the squeegy. In terms of its longevity I cannot say as that caravan was sold within a few months of fitting the film, and it wasn't really exposed to summer sun.
I am not sure how well it would go onto a large front window. Certainly on the large single front window I wouldn't entertain it on the grounds of installing over such large area which does have some curvature and flexibilty. A single piece of film will have a mind of its own. There is also the practicality of removing it when the van is sold, as it may not be attractive to future owners. Two other points come to mind and although these aren't based on experience I will risk a rap on the knuckles.
1. As you head south to warmer climes having large reflective mirror in your rear view, could require re-orienating the cars mirror. Does that affect other things that you rely on when towing.
2. Similarly towing at night will reflect brake lights and again may necessitate re-orientating the driving mirror.
On hot days here or abroad we managed fine with the caravan blinds/opening the window etc as described by others above.