While we've never been turned away (when we owned a 10+ year old rig) friends have.
But, ours was parked under cover, clean and well maintained.
Theirs had moss and mildew. Also the main awning had been torn off.
The "age" rule is a way to turn away poorly maintained rigs.
2008 F350SD V10 with an 2012 Arctic Fox 29-5E
When someone tells you to buy the same rig they own, listen, they might be right. When they tell you to buy a different rig then they own, really pay attention, they probably know something you don't.