Tires break down in various ways. The most common is UV degredation which takes its toll on rubber. The cracking and crazing is a result of that and if you keep the car outside in sunlight it will deteriorate faster. There are dressings you can put on your tires that will block UV and help preserve the tires and keep them from "Dry Rot". I also cover the tires when not in use further blocking UV light. I have a friend at Firestone ( He is looking for another job) and he indicated that if properly stored the tires can last many many years (beyond 20). But no matter what you do the tires will still deteriorate at some rate. I have a car with 5,000 miles on it and the NCT's are original. They are in excellent shape and I have no problem driving them. They are not that stiff either. I did go 900 miles to the Nashville show and do about 200 miles a year although my car now is more of a trailer queen. I have however seen NCT tires that have cracks and are stiff. Those tires I would not feel safe on. Overall if you are not showing the car in concourse events and if it were mine I would put on a set of Yokahama tires and enjoy a smoother ride. Just my opinion Ken <A HREF="http://deloreancarshow.com">DeLorean Car Show</A>