Deregulation and competitive nature of electric power industry have forced the utilities to optimize the operation and the maintenance cycles of their assets to extend their life time and to minimize the total costs. This paper is an extension of a recent study and aims to increase the improvements in the reliability parameters and total lifecycle of the power transformers of Turkish National Power Transmission System. This extension covers the possible failure rate decreases as a result of decrease test rates. Once the consideration of the parametric analysis is described, the effect of the failure rate changes on the reliability indices is determined as a result of the maintenance improvement in addition to test to operation and failure to operation rates determined previous study. Also, the sensitivity analysis is performed.