Whatever floats your boat, but for me, I keep the mattresses on. I find that the folded mattress actually helps avoid canvas getting caught in the seals. Once you tuck the canvas behind the mattress as you are raising the bunk door, it actually pushes the canvas into the trailer and away from the seals. I took the mattresses off recently to facilitate a minor repair and man, it was a pain in the butt. They are bulky and awkward to deal with. I can't imagine doing it for every trip, but that's just me.
Michael, Cristina, Anthony, Cocoa Puff, Cookie, Blossom, Tosca, & Heidi
2012 Rockwood Roo 21SS