The sun does a number on them covered storage is the best way to protect your investment. Dries out the caulking and rubber roof, fades the paint and graphics, dries out and cracks the tires. Dries out and shrinks the rubber around the windows. If the sun isn't blocked coming in the windows fades the interior. Makes all the exterior plastic yellow and brittle. Fiberglass oxidation. Fades all exterior lighting. Dries out and destroys the awning material.
How do I know this? I bought a used trailer from Florida that was 5 years old, never again.