Multistage Interconnection Networks (MINs) are a cost-effective idea for connection between different nodes in multi-processor systems. In the meantime, understanding the impact of increasing the number of stages (i.e. a famous method for improving fault tolerance) on the reliability of these networks is essential. Last studies on this challenging issue, revealed that adding one switching stage to MINs is preferable to two in terms of reliability. However, there were some non-negligible gaps in previous researches: (i) The probability of failure for terminal nodes was not considered in the calculation of reliability. (ii) Numerical results were only based on the small size of the network, i.e. 8 × 8. (iii) Reliability analyses were time-independent. (iv) The lack of some important parameters such as the mean time to failure and availability was noticeable. Therefore, this paper will take a more comprehensive analysis of reliability to meet the above specifications.