When it comes to lasting a long time, I doubt that any of the non-aluminum skinned trailers will last as long as the Avion, Airstream, Silver Streak, etc., type trailers. Those old style trailers were expensive and labor intensive to build, but the shells would last for many generations, even if they were left out in the elements. It is the wood floors that you have to worry about, and most of those can be fixed, if there were problems. Some of them had better frames than others so the ones with the long lasting shell with the strongest frames should last the longest.