I know that we love the stories of 27+ year old tyres being 'trimmed' for use when the reinforcement starts to show through the surface rubber, but the events here in the UK last year focused on tyre age - even though it was not a factor in the accident that occured at 280 mph.
Tyres or the materials they are made from have a life - be they road or track. Know the age of production (which may be some years before the purchase date) and do not use them beyond the stated period would be the health and safety ruling.
Shipping methods, handling, mounting, storage and 'running in' are all factors that can affect the speed capability. A brief chapter in the Dieselmax book (search Amazon) tells us how JCB went about protecting Andy Green.
Tyres are a small percentage of the cost of most vehicles so do not play cheap with the only contact between you and the salt.