Personally I am concerned about tire "rot". I have had a couple of experiences to reinforce those concerns.
I had a spare tire stored under the truck bed for 4 years. It seemed like a good idea to pair it up with a new tire of the same make. It appeared to be in good shape but within a few weeks and only a few miles of use, it showed signs of deterioration with cracks developing on the side walls.
I have a 2015 Honda Accord with low mileage. I just had to replace the tires to severe dry rot which I was not visible a few months ago.
Now I am watching the dry rotting of my Ram 3500 tires. They are low mileage and exactly 6 years old. A few weeks ago I noticed minor cracking in the area around the tread. I did not seem like a big deal. Now, almost daily, I can watch the cracks developing on the sidewalls. Due to medical issues I will not be using the truck for a couple of months. I am going to continue to watch these cracks deepen and become more visible.
I have concluded that there can be no signs of dry rot and then a rapid progression. BTW, it is not just age but lack of use that contributes to dry rot.