Mine is a 2012 (see signature), one year older than yours. I just replaced my tires a few months ago. I'm definitely in the camp with 'replace them after 7 years regardless'. As several have indicated, yes, you might get more than 7 years, but IMO the price for a tire failure with these rigs is just too great, and not worth the risk.
Also, when you put new tires on, have them check the alignment! When I replaced my tires a few months ago, I had noticed fronts were wearing excessively on outside edges. They found the toe-in was waaaaay off, had been that way from the factory! Had them correct that, Motorhome drives muuuch better now, much more straight! All those years I drove thing thing and thought its wandering was just the way it was with these rigs, didn't realize all it needed was an alignment. Now, its much less effort to drive, not near as much steering input needed. :)