Don't know if you are buying new or used but I can tell you on a used one they get tired.
And here is why. The under carriage of the frame is mostly plywood framing, particle board and a couple of 1x's. Which over time sags and splits and pulls apart where it is attached to the wall was just a joke.
I had an RV Mobile Repair guy point that out to me. He took the whole couch out and rebuilt a new frame with 2x4's and changed out how it was attached to the walls.
What a BIG difference in comfort when opened and closed.