I own a 2014 ECON 16RB. We purchased new in Oct 2013 and just recently had a structural issue due to water intrusion.
The front cap started pulling away at the lower curb side. Took it to a highly regarded local fiberglass repair shop for repairs. They felt the frame should have more structure out to the edges at the very front for better support. They also noted that the cargo hatches no longer sealed and probably allowed water intrusion during rain.
They fabbed up some additional support brackets for the front and welded to the frame. They also replaced the seals on the cargo hatches.
No other issues with the unit. I keep a towing log and have recorded that we have towed the unit 20,395 miles since purchasing. We have spent 148 nights in the unit in the past 5 years as well.
I have no idea how that compares with "typical" usage or miles towed.
Good luck with your unit. Overall we're happy. Everything inside has been solid.
Rick & Kathy
2014 Econ 16RB
2013 Nissan Titan Crew Cab