Goodyear Duratrac tires are specifically designed with an average life span of about 50000/80000 miles, that is if load limit is not exceeded.
And if we are to translate this distance/mile coverage into time, it should serve for an equivalent of about 4 to 5 years for a properly used car.
Our assumption only holds for absolute condition, but in the real world we knew things are far from absolute.
Bad road conditions and hazards on road like spike, nails and screws may affect the normal tire lifespan. Failure to stick to and maintain healthy and proper routine can adversely affects the lifespan of tires.