Industrial systems are in general subject to deterioration, ultimately leading to failure, and therefore require maintenance. Due to increasing possibilities to monitor, store, and analyze conditions, condition-based maintenance policies are gaining popularity. The most detailed approach for modeling condition parameters is by using continuous-time continuous-state stochastic processes. However, the resulting analysis can be quite difficult, and therefore simulation is often used. We describe an approach for discretizing continuous-time continuous-state non-decreasing deterioration processes, resulting in discrete-time Markov chains. Furthermore, we show how standard matrix algebra can be used to optimize condition-based maintenance policies, taking into account a required planning time for carrying out maintenance.