How often do you replace the tires on your seldom driven muscle cars? When they look like new with no signs of dry rot it's hard to just toss them,even though you know you probably should.I've got some like new TA's that have been on since the mid 90's and I know I probably need to replace them. How often do ya'll replace?

I work in the tire and wheel industry and I have been told for safety reasons, to replace tires every 5 years no matter the mileage.

That statement might be a marketing ploy, but the fact is, most people do not know how long our tires have been sitting in a warehouse or in the back of a truck, on a ship, or in a store before you own them for that 5 year period, unless you know how to look up the date of when the tire was made.
I am sure that allot of us have driven on tires in the past that were more than 5 years old (from purchase date), but that is a good time reference to start inspecting your tires. With the initial expense of a set of tires, I would bet that allot of us with these old cars probably wait longer than 5 years to buy a new set.

Also in the tire business, goverment was trying to get a 6 year band on tires for a while, but haven't heard much lately. Commen sence, look for dry rot or cracking, on side walls and in the tread area, my wifes Z has a little over 1,000 miles in 10 years and tires still look great and I,m not going to change them until I see a problem with them, so I would just inspect them offen.

If I understand correctly, the issue with cracks is that it allows moisture into the carcass and can allow the steel belts to rust and therefore weaken, yes?

So if no cracking, what other issues are there? The tires crack due to UV light, right? So the inside of the tire should not crack?

the concern with cracks is that when they get bigger you are going to start losing air and the area becomes weaker, little surface cracks are usally not a problem, it's when they start growing than it's a smart thing to take them off. Tires that are outside all the will have more problems