K Charles wrote:
They set outside the factory without a cover and then at the dealer without a cover.
That's an irrelevant argument - no manufacturer, no dealer is going to invest in hundreds of trailer covers, then pay someone to install them and then later again to remove them from trailers that are only going to be sold anyway. :S Whether made to be outdoors or not the reality is that in harsh winter climates the roof and especially the many roof seals are exposed not only to snow but the effects of that snow repeatedly melting then turning to ice then melting then turning ice again. :E This same process applies to the awning as well, especially in the trough formed where it's affixed to the trailer. Using a breathable cover provides a barrier between the seals & awning and that constant melt / freeze cycle. Our popups I always stored indoors but I've winter covered every full height trailer we've owned and wouldn't ever consider not covering, even if stored in a campground where I'd have to tow it from the storage lot to the campsite for use ... at low campground speeds it's a non-issue.