We also went through the FMCA Michelin tire program with our previous 2008 coach changing out all 8 tires in May of 2013 with tires dated 2006-4206 (7 yr. old tires). I received $50 each for the take-off's. A good deal all the way around.
Seven years is my personal limit as my old tires still had a little value and good tread with 57,000 miles. I knew that we were going to change coaches so I got to use the new tires for 1.5 yrs. before we sold it. It also gave value to our coach because of the newer tires.
Goodyear tires rivering just don't give me the warm fuzzy's. It seems tread wear like rivering would also build up heat as that has to stress the tire (only a logical observation not technical).
Taking tires to the maximum life just doesn't seem safe to me and that would be all I would be thinking about... a blow-out.
Everybody has their comfort level, I'm with the OP, he did good.
MM.