I used two in our old Ford and they worked pretty well...SMALL AREA
, also in an unheated closet. I think you would need at least 1/2 dozen to do any good in a 25' AS.
BUT....you haven't given us enough info. AS size, location etc.
Here in WNY, Winter cold doesn't necessarily mean high humidity, as the inside humidity rises I use a Pelonis 1500w to help keep inside temp above the dew point.
Raining hard today....
POI...with the AS plugged in, and a proper 3 or 4 stage converter upgrade, the batts will stay charged if they are left installed thru the Winter. Regular checks recommended.
"Sticks & stones can break your bones...and hail will dent your Airstream"
So when is this..."old enough to know better" supposed to kick in?