Thank You Mike/PAX for sharing the link. It was quite interesting.
Unless I missed it, there was no mention that tires need replacing after a certain age. Replacement of tires exclusively involved their physical condition. Therefore I feel our perfect condition 10 year old Michelin tires are still good to use.
Funny, they mentioned how the front tires can get worn unevenly, "feathered edges", due to wheel alignment issues. I have some front tire thread feathered edges as he described, but I feel it is caused by strong & consistent side winds for days at a time driving across the Great Plains, having my steering wheel pointed to the left or right pending the direction of the consistent blast of air to keep the rig going straight.