Tire Dry Rot or Not

I was a bit sad last week when I opted to replace my deep treaded Bridgestones for new ones when upon close inspection I observed the beginnings of dry rot ... about the same stage as the ones in your photo. I carry loads and kids so I am more inclined to play it safe. The truck is parked outdoors most of the time so I'm more likely now to toss a cover on the sunny side tires when parked in the driveway now. I'll keep the old tires and apply a little dressing to perhaps prolong their remaining life and use during Winter/snow or something. Tires approx 8 yrs old and 25k miles