Had an appointment yesterday to pick up a couple of Maxxis' 8008's for my cargo trailer at a local tire shop chain. Before the install I insisted on checking the DOT Codes and was glad I did...
The tires were manufactured in April of 2016, more than 4 years old.

I asked their manager where they got off trying to sell me 4+ year old tires as new and all I got was the deer in the headlights stare and a lame, mumbled "sorry'. No, I won't be back!
Last fall I had a 5.5 year old Michelin LT grenade on my Class C west of Phoenix on I-10. I had had my tires inspected and aired up for their respective loads the previous day by Discount tires who reported they were fine. That "fine" tire did $4,131 in damage to my coach literally blowing the wheel well right up through the floor.
It is usually not the miles or apparent wear that leads to a failure, tires time out and I will NEVER own a tire more than 5 years old again. I do admit that southern Arizona is a tougher venue than most on tires. I had a China Bomb shred on my 22' TT about 8 years ago, went out and replaced all 4 with Maxxis' 8008 the next day... that was the end of the problem.