That 10 year thing gives campgrounds the opportunity to turn away junkers. Like a 25 year old TT with a house a/c unit hanging off the side...or any RV with wood where windows should be. Or something that looks as bad as some of the "seasonal" people at campgrounds.
Never heard of it being enforced...howwever, I'm sure sometime, someone did. Rememeber that super-duper Class A (Prevost)RV resort that turned away a new $300,000 class C some years ago?
Just keep what you got clean and looking good...should be no problem. And...if for some dumb reason they say "no"....go right down the road. Someone else would be happy to take your money.