The life of a tire cannot be measured by miles alone. Tires are composed of various types of material and rubber compounds, having performance properties essential to the proper functioning of the tire itself. These component properties evolve over time. For each tire, this evolution depends upon many factors such as weather, storage conditions, and conditions of use (load, speed, inflation pressure, maintenance etc.) to which the tire is subjected throughout its life. This service-related evolution varies widely so that accurately predicting the serviceable life of any specific tire in advance is not possible.
It is impossible to predict when tires should be replaced based on their calendar age alone. However the older a tire, the greater the chance that it will need to be replaced due to the service-related evolution or other conditions found upon inspection or detected during use.
While most tires will need replacement before they achieve 10 years, it is recommended that any tires in service 10 years or more from the date of manufacture, including spare tires, be replaced with new tires as a simple precaution even if such tires appear serviceable and even if they have not reached the legal wear limit.
The warranty covers defects in workmanship and material for the life of the tread or 6 years from the date of purchase, whichever occurs first. With no proof of purchase, the warranty period is for 6 years from the date of manufacture (this is indicated in the DOT # on the sidewall).