1. A method of managing semiconductor manufacturing defects, the method comprising: determining a cumulative aging parameter for each of a plurality of first IC products produced with a particular manufacturing line, the cumulative aging parameter being dependent on a product operating condition; calculating an observed defect rate for the plurality of first IC products based on a difference between a predicted value of the aging parameter and the cumulative aging parameter for each of the plurality of first IC products; and adjusting a manufacturing reliability model for the particular manufacturing line in response to the observed defect rate being different from a predicted defect rate for the plurality of first IC products.