I'm not saying yes or no. Just something I've noticed over 30 years of working in MC dealerships. Tires we had in stock for over a year were harder than the same exact brand and model tire we just got in. When mounting these older tires, the rubber was harder and stiffer than the newer ones. I've also noticed this to be true with the front tire on my bike now, Dunlop D606. It's about 3 years old now and so hard, I can ride it with no air and I have with a flat and didn't notice it. I found it had no air only due to my regular maintenance checks. Yes, that stiff. I'm changing it out for a different tire in a week or so. Not cuz its stiff, but because I don't like that tire. So keep in mind, an older tire due to its durometer reading (hard or soft) may not perform like you expect even though it's not dry rotted or appears to be ok. I'm just sayin....

 

Bagged and sealed, yes but most inexpensive tires are not stored that way. After five years a tire "hardens" because of the natural chemical evaporation from the tire. After five years there is a noticeable performance drop compared to a new tire. I was a tire Goodyear tire dealer for 15 years.