The life of your tires is dependent on many factors, including driving habits, road conditions, vehicle loading, inflation pressure, maintenance history, speed, and environmental conditions (even when the tires are not in use).
In addition to regular inspections and inflation pressure maintenance, it is recommended that you have annual inspections performed once the tires reach five years old. All tires, including the spare, should be removed from service after 10 years from the date of manufacture, regardless of their condition or state of wear.