We bought a Flagstaff that was about 3 years old in 2007, and kept it for 9 years. It was was garage kept almost its entire life. We never had any problems with it, and we had a great time in it.
It had A/C that worked great, only struggled one trip, we had no shade and it was about 100 degrees and humid. Also had a furnace, and heated mattresses.
It was probably one of the best purchases we ever made. We paid $6000 for it, and sold it for $5000 after 9 years, and we made priceless memories with the kids.
Coleman made some good ones but did have some roof issues on some models. If you google Coleman ABS roof issues you can find the info. Sorry I don't remember the years and models that had the problems.
As others have said the care taken by the owner is probably more important than brand.