Tires:
The rubber plantations burned in the late 90's.
Ever since, the % of actual rubber in a tire has gone down. They barely use it for belts and hoses anymore.
Look at a new tire. There is a date code on it.
They added more detailed date codes: that's right, when they started reducing rubber %.
Some brands are better than others. Sometimes the tire construction vs the use means you can get away with some older tires. I have 2008 on my Dakota, they are cracked up, but the cracks haven't gotten worse and nothing is vibrating. Previous owner put them on when his factory goodyears from 98 went bald after 35k miles and then proceeded to put 15k miles on these pirelli scorpio(n?) AT's over the next 15 years. So they look like new. Except they cracked all up. I just bum this truck around, go to work, etc. No big loads, the tires are rated for half ton payloads. I am not to worried.
New tires have a 5 year expiration date. That is all the longer the manufacturer will be liable for in case of failure. Same with whoever installed them. If they look like new or not, tough.
In fact, if you take your car to some of the box store tire places, they may refuse to service the tires, or do an alignment if your tires are "expired".
Tires from the 90's, 80's, 70's.... they are made of rubber. The factory spare from my 78 Monaco looks like it is 2 years old. No cracks. The whitewall Continental's that came on the Monaco are from 1996. No cracks. Fugly wheels, but they will make nice rollers for projects for me until I am dead.
Some manufacturers make a better tire with more rubber. You can usually tell by the price if it is a "normal" size, like a 275/60/15.
Truly, "they don't make them like they used to". Tires have become globalized and consolidated like everything else. Michelin owns BFG. Firestone owns Bridgestone. Goodyear owns Kelly, Dunlop, few others.
The one in Canada makes Cooper, Mastercraft, etc.
Tires, like most everything else, have fallen prey to the "throw it out and buy new" planned obsolecence crap we have in everything.
Baby new tires if you can to keep them nice, keep them out of UV and in a moderate temperature. Just remember if you have them for 6 years with 5k miles on them and run a nail over the tire shop will tell you too bad.
My policy is:
Cracks starting to show on my seasonal ride? RIGHTEOUS BURNOUTS FOR EVERYONE. No sense throwing out a tire with 80% tread that blew out the sidewall to dryrot after 5-6 years.
As for concrete, NEW concrete has additives that did not exist in OLD concrete. I have never had a tire crack up sitting in my 1970's era shop or garage, or in the 1998 storage shed for that matter.
I have seen and been warned from tractor dealerships and the local tire shop that new concrete+ tractor tire = cracked out to trash in about 1 year. New concrete sucks the life out of tires. You have two choices:
Seal it with a product(epoxy coat)
Put something between tires and floor. Sheet of plywood is the easiest.
Later on once enough dirt has been on it and whatever leeches out of the floor, it won't matter so much. But if your floor is the "shiny new grey" it probably isn't safe yet.