A notable requirement of heterogeneous parallel and distributed computing systems is to maximize their processing performance and agreed upon QoS. Lots of work in this field has been done to optimize the system performance by improving certain metrics such as reliability, robustness, security, and so on. However, most of them assume that systems are running without interruption all the time and seldom consider the system's intrinsic characteristics, such as failure rate, repair rate, and lifetime. In this paper, we study how to achieve high availability based on residual lifetime analysis for heterogeneous distributed computational systems with considering their essential features. First, we provide an availability model taking into account system's expected residual lifetime. Second, we propose an objective function about the model and develop a heuristic scheduling algorithm to maximize the availability with the makespan constraint. At last, we demonstrate these advantages through the extensive simulated experiments.