good camping friends have a 2009 5th wheel, probably 50K + miles on it, still in excellent shape, our 32ft TT (outback with opposing slides) bought new in 2010 with close to 45K miles on it still in excellent shape no issues.
Since we seldom use RV parks can't answer the "10 year" question, but on a few occasions when asked I just say "take a look" and they give the trailer a pass since it has no faded decals, no cracking decals, etc. since we keep it covered in the winter.
I've never seen a state/county/BLM/FS or other public campground that had an age requirement for trailers. Seems to be a "high end" "luxury" RV park that has the age limits.
