We had a Trillium
4500 for 20 years on our property 7/8 mile from the water's edge in northern California, very similar to so. Oregon. You want to protect your trailer from the weather, both from the salt air and rain and from the UV in the sunlight. Rust and corrosion are a problem, but manageable if the the trailer is kept under cover. The other problem is mold and mildew from the high humidity. We used an inexpensive portable carport (like from Walmart or Costco) for a few years; it worked well until the steel frame rusted away, the fabric was still fine. After that we went with a pre-fab steel carport on a slab, which did great for protecting the Trillium
and shows no sign of deterioration after 10 years. If you can have power, I would recommend running a dehumidifier if you are not using the trailer.