Our experience has been that a lot of Parks have the rule but only use it to keep out the run down RV's.
While in Las Vegas at the Las Vegas Motorcoach Resort, I saw an old Bluebird that was at least 25 yrs old. Beautiful coach. They have a 10 yr. rule but will make exceptions.
A guy in our Prevost group has a 2004 Liberty Coach (Liberty Coach put their series number painted on the door and drivers side), for example... Our says: "Liberty Elegant Lady Series 2015", which indicates it's a 2015 model.
This guy had his 'Series 2004' changed to 'Series 2014'. He did this so that he wouldn't be questioned about it being over 10 yrs. old. Honestly, most Prevost coaches are hard to tell their age. His certainly doesn't look 12 yrs. old.
MM.