The test method for evaluating image stability at dark storage condition specified in the ISO standard on the Arrhenius law. In the previous three papers on this series reported at the 1998, 2001 & 2003 SPSTJ annual conferences, the author reported a time-saving procedure utilizing programmed temperature/humidity cycles. The method has been further refined by introducing a new technique “analysis extrapolating profile” The details will be discussed in the present report.