Our first TT held up well for 16 years of once per month travel plus several week to 2 week long trips each year along with one 5000 mile cross country trip. It was still in great shape when we sold it.
Our current 5th wheel is 21 years old and has traveled similar trips to above. It looks near new.
Both trailers had very few problems that would be attributable to build quality. Most problems were due to wear and tear.
Both were mid level quality RVs. Great value for the price.
I do maintain and perform routine preventative maintenance on all of my vehicles.
Like DutchMan Sport posted...upkeep is the key to longevity.