One of the important applications of software reliability models is the determination of software release time. Most of the existing studies on this topic use models based on non homogeneous Poisson process with a bounded mean value function. Multi up gradation based software reliability growth model is developed for successive release modelling and analysis. Based on this model, maximum fault removal for upgraded software and optimal release time of upgraded software are investigated as well. This paper proposes a new practical method for determining when to stop software testing considering failure intensity and cost as two factors simultaneously. This issue has been widely known as the optimal release problem of software product. The proposed new decision model based on multi-attribute utility analysis is tested on the real world data sets. In addition, the proposed decision model can help companies to make a rational decision on the optimal timing of the software.