Whether a non-airstream unit is a throw-away trailer is dependent upon upkeep and maintenance through it's lifespan. I always manage to see quite a few very old non-airstream rigs every time I go camping that appear to be going strong, but I doubt I will keep our current 6 year old RV more than 10 years.
I've known neighbors who went from an airstream to conventional and from conventional to an airstream as there are pros and cons to either choice. As for us, my DW and I don't have any designs of owning an airstream in the future, but that's due to our personal tastes. They are no doubt durable units, but not our cup of tea so to speak.