I installed 4 Maxxair II's last year, as soon as I got the trailer.
The vents have been open since then, even in the winter, while not in use.
No problems, except once, when some hornets tried to build a nest in it.
2012 Jayco Eagle 365BHS
2012 Silverado 2500HD CC Z71 Duramax/Allison
Curt Q20 Hitch with Roller
Firestone Ride-Rite Air Springs