Elastomers are employed within critical components of deep water oil production systems designed for twenty to fifty years’ service. Elastomer properties are influenced by chemical changes, collectively identified as ageing processes, that occur over time. Time / temperature reaction rate (Arrhenius) transformation applied to controlled ageing experiments provides a conservative means of characterizing the long-term ageing effects. In this study, several different experimental techniques for obtaining the necessary measurements of accelerated material behavior are employed and compared. Various analytical techniques for characterizing rates of change over time and across temperatures are applied to the measured data. Significantly different results are obtained depending upon the choice of assumptions. Variation in results depend upon accelerated ageing temperatures, the relative availability of oxygen to the test specimen during ageing, and the size of the test specimen.