In a recent paper Iskandar ＆ Sandoh (1999) studied an opportunity-based age replacement policy for a system which has a warranty period (0,S]. When the system fails at age x $leq$ S a minimal repair is performed. If an opportunity occurs to the system at age x, S $leq$ x $leq$ T, we take the opportunity with probability p to preventively replace the system, while we conduct a corrective .replacement when its fails in (S,T). Finally, if its age reaches T, we perform a preventive replacement, Under this policy the design variable is T. For the case when opportunities occur according to a homogeneous Poisson process, the long-run average cost of this policy was formulated and studied analytically by Iskandar & Sandoh (1999). The same problem is here analysed by using a graphical technique based on scaled TTT-transforms. This technique gives, among other things, excellent possibilities for different types of sensitivity analysis. We also extend the discussion to the situation when we have to estimate T based on times to failure.