All brands of campers have their good ones and their lemons. All the brands you mentioned are about equal in quality and reputation. Airstream still stands a head above the rest though.
For almost every camper, once it reaches 1 year old, there is no more warranty left from the manufacturer. Remember, the manufacturer is the company that assembles the parts. If the parts are still holding together after 1 year, then the camper (in all practical reality) has survived it's life time.
Now each individual part will also have it's own manufacturer warranty, which is usually longer than 1 year. The trailer frame will usually be warrantied for 5 years, the oven 2 years, the refrigerator 5 years, and so on. If you have an issue with the "parts" you have to fight the "part" manufacturer, not the RV manufacturer.
And then, when everything reaches a certain age, you are simply on your own if something gets broken or needs replaced from wear and tear.
Age in a camper (of any kind) does not mean anything either! What does matter is how well the previous owner kept the camper and maintained it. A 1 year old camper can be a hunk of junk if the owner abused it and did nothing to take care of it and maintain it. A 30 year old camper may look aged and dated, but may be in immaculate shape if the owner took care of it and fixed thing when things needed fixing.
To answer your question, there is no single bullet answer. You have to examine every camper you are considering for the merit of that camper.
One word of advise about purchasing anything, especially off the internet ... never, never, never purchase an RV without first seeing it yourself and have the owner turn on and run everything first. Including dumping the tanks. Make sure the tanks are empty when you buy it.