There are probably hundreds of thousands of aluminum spars on sailboats around the world existing in a marine environment. All aluminum hulls, too. With stainless steel fittings attached with SS screws. Some have brass and copper attached, also.
No building material lasts forever. But with proper maintenance, any of them will probably outlast you.
The Starstream is pretty cool looking. From a quick search, it seems the walls, floor, and roof are Al framed, styrofoam panels with luaun on both sides. The roof and walls are skinned with Al with a “special” coating similar to an automobile finish.